NEWZEALAND
3^ EDICT OF GOVERNMENT "^l
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AS-NZS 3500-3 (2003) (English) : Plumbing and
drainage - Part 3: Stormwater drainage [By Authority
of New South Wales Code of Practice - Plumbing and
Drainage]
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AS/NZS 3500.3:2003
(Incorporating Amendment Nos 1 and 2)
(A3 appended)
STAIMDARDS
N E \A/ ZEALAND
PAEREWA A or E A R OA
Australian/New Zealand Standard™
Plumbing and drainage
Part 3: Stormwater drainage
STANDARDS
AS/NZS 3500.3:2003
This Joint Australian/New Zealand Standard was prepared by Joint Technical
Committee WS-014, Plumbing and drainage. It was approved on behalf of the
Council of Standards Australia on I November 2003 and on behalf of the Council
of Standards New Zealand on 19 November 2003.
This Standard was published on 15 December 2003.
The following are represented on Committee WS-014:
Association of Accredited Certification Bodies
Association of Consulting Engineers Australia
Association of Hydraulic Services Consultants Australia
Australian Industry Group
Australian Steel Institute
Building Officials Institute of New Zealand
Business New Zealand
Department of Infrastructure, Energy and Resources (Tasmania)
Engineers Australia
Housing Industry Association
Master Plumbers, Gastltters and Drainlayers New Zealand
Plastics Industry Pipe Association of Australia
Plastics New Zealand
Plumbing Industry Commission
Keeping Standards up-to-date
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may have been published since the Standard was purchased.
Detailed information about joint Australian/New Zealand Standards can be found by
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Standards Australia or Standards New Zealand at the address shown on the back
cover.
This Standard was issued in draft, form for comment as DR 03 198.
AS/NZS 3500.3:2003
(Incorporating Amendment Nos 1 and 2)
Australian/New Zealand Standard
Plumbing and drainage
Part 3; Stormwater drainage
TM
Originated as part of AS CS 3—1931.
Previous edition AS/NZS 3500.3.2:1998.
Jointly revised and redesignated as AS/NZS 3500.3:2003.
Reissued incorporating Amendment No. 1 (July 2006).
Reissued incorporating Amendment No. 2 (March 2010).
COPYRIGHT
© Standards Australia/Standards New Zealand
Ail rights are reserved. No part of this work may be reproduced or copied in any form or by
any means, electronic or mechanical, including photocopying, without the written
permission of the publisher.
Jointly published by Standards Australia, GPO Box 476, Sydney, NSW 2001 and Standards
New Zealand, Private Bag 2439, Wellington 6140
ISBN 7337 5604 2
AS/N/.S 3500.3:2003
PREFACE
This Standard was prepared by the Joint Standards Australia/Standards New Zealand
Committee WS-020, Stormwater, to supersede AS/NZS 3500.3.2— 1998, National
Plumbing and Drainage, Part 3.2: S/ormwater drainage— Acceptable solution.
This Standard incorporates Amendment No. I (July 2006) and Amendment No. 2 (March
2010). The changes required by the Amendment are indicated in the text by a marginal bar
and amendment number against the clause, note, table, figure or part thereof affected.
The objective of this Standard is to provide installers with solutions to comply with —
(a) the Plumbing Code of Australia (PCA);
(b) the Building Code of Australia (BCA); and
(c) the Building Code of New Zealand for stormwater drainage.
This Standard is part of a series for plumbing and drainage, as follows:
AS/NZS
3500 Plumbing and drainage
3500.0 PartO: Glossary of terms
3500.1 Parti: Water services.
3500.2 Part 2: Sanitary plumbing and drainage systems
3500.3 Part 3: Stormwater drainage systems (this Standard)
3500.4 Part 4: Heated water services.
3500.5 Part 5: Domestic installations
This revision includes the following changes:
(i) Changes in the context to enable this Standard to be referenced in the above listed
Codes.
(ii) The inclusion of revised clauses to bring them into line with the provisions of the
Plumbing Code of Australia.
(ii) Revision of the materials and products used in stormwater drainage systems.
(iii) Incorporation of Amendment 1 and RUL PL. 13 — 2002.
(iv) Revised examples in Appendix H.
Other changes incorporate amendments and additions arising from industry
recommendations which include —
(a) changes in limitations in FRC pipes and epoxy resins; and
(b) clarification of examples for design of eaves gutters of slope less than 1 :500.
This Standard does not cover the criteria for soakers and siphonic systems. Sufficient data
was not available in these areas at the time of publication. These areas will be included in a
future edition of this Standard, subject to additional research and investigation being carried
out.
The terms 'normative' and 'informative' have been used in this Standard to define the
application of the appendix to which they apply. A 'normative' appendix is an integral part
of a Standard, whereas an 'informative' appendix is only for information and guidance.
Statements expressed in mandatory terms in notes to figures and tables are deemed to be
requirements of this Standard.
PROVISION FOR REVISION
AS/NZS 3500.3:2003
This Standard necessarily deals with existing conditions, but is not intended to discourage
innovation or to exclude materials, equipment and methods, which may be developed in
future. Revisions will be made from time to time in view of such developments and
amendments to this edition will be made only when absolutely necessary.
AS/NZS 3500.3:2003
CONTENTS
Page
SECTION I SCOPE AND GENERAL
1 .1 SCOPE AND APPLICATION 7
1 .2 REFERENCED DOCUMENTS 7
\3 DEFINITIONS 7
1.4 NOTATION 9
L5 IDENTIFICATION 12
1 .6 PROTECTION OF WORKS 12
1.7 DISCHARGE POINT CRITERIA 13
SECTION 2 MATERIALS AND PRODUCTS
2.1 SCOPE OF SECTION 14
2.2 AUTHORIZATION 14
2.3 SELECTION AND USE 14
2.4 ROOF DRAINAGE SYSTEM 14
2.5 STORMWATER DRAINS (NON-PRESSURE) 15
2.6 RISING MAINS (PRESSURE) 16
2.7 SUBSOIL DRAINS 16
2.8 .lOINTS 16
2.9 VALVES 18
2.10 CONCRETE AND MORTAR 18
2.1 I EMBEDMENT MATERIAL 19
2.12 TRENCH FILL 19
2.13 MISCELLANEOUS 19
2.14 FILTERS FOR SUBSOIL DRAINS 20
SECTION 3 ROOF DRAINAGE SYSTEMS DESIGN
3.1 SCOPE OF SECTION 21
3.2 GENERAL METHOD 21
3.3 METEOROLOGICAL CRITERIA ...21
3.4 CATCHMENT AREA 22
3.5 EAVES GUTTER SYSTEMS 27
3.6 VALLEY GUTTERS 32
3.7 BOX GUTTER SYSTEMS 33
3.8 SOAKERS 35
SECTION 4 ROOF DRAINAGE SYSTEMS—INSTALLATIONS
4.1 SCOPE OF SECTION 42
4.2 TRANSPORT, HANDLING AND STORAGE 42
4.3 THERMAL VARIATION 42
4.4 CORROSION 43
4.5 INSTALLATION AND TESTING 44
4.6 INSPECTION AND CLEANING 47
4.7 ALTERATIONS AND DISCONNECTION 47
4.8 EAVES GUTTERS 47
4.9 BOX GUTTERS 47
4.10 VALLEY GUTTERS 48
4.11 DOWNPIPES 48
4.12 OVERFLOW DEVICES OR MEASURES 49
4.13 .lOINTS FOR METAL COMPONENTS 49
AS/NZS 3500.3:2003
4.14 JOINTS FOR PVC COMPONENTS 50
4.15 JOINTS FOR OTHER COMPONENTS 50
4.16 SUPPORT SYSTEMS 52
SECTION 5 SURFACE DRAINAGE SYSTEMS—DESIGN
5.1 SCOPE OF SECTION 54
5.2 DESIGN METHODS 54
5.3 LAYOUT 54
5.4 GENERAL METHOD 56
5.5 NOMINAL METHOD 68
SECTION 6 SUBSOIL DRAINAGE SYSTEMS—DESIGN 69
SECTION 7 SURFACE AND SUBSOIL DRAINAGE SYSTEMS— INSTALLATION
7.1 SCOPE OF SECTION 70
7.2 GENERAL REQUIREMENTS 70
7.3 SITE STORMWATER DRAINS 75
7.4 SUBSOIL DRAINS 79
SECTION 8 SURFACE AND SUBSOIL DRAINAGE SYSTEMS— ANCILLAR I ES
8.1 SCOPE OF SECTION 81
8.2 PAVED SURFACES 81
8.3 POINT(S) OF CONNECTION 81
8.4 REFLUX VALVES 81
8.5 INSPECTION OPENINGS 82
8.6 STORMWATER PITS, INLET PITS AND ARRESTERS 82
8.7 SURCHARGE OUTLETS 88
8.8 JUNCTIONS 88
8.9 JUMP-UPS 89
8.10 ANCHOR BLOCKS 90
8.11 ON-SITE STORMWATER DETENTION (OSD) SYSTEMS 91
SECTION 9 PUMPED SYSTEMS
9.1 SCOPE OF SECTION 94
9.2 GENERAL 94
9.3 WET WELLS 94
9.4 PUMPS 95
9.5 RISING MAINS 95
9.6 ELECTRICAL CONNECTION 95
SECTION 10 SITE TESTING
10.1 SCOPE OF SECTION 96
10.2 DOWNPIPES, SITE STORMWATER DRAINS AND DRAINS WITHIN OR
UNDER BUILDINGS 96
10.3 TEST CRITERIA 96
10.4 PROCEDURE 97
APPENDICES
A REFERENCED AND RELATED DOCUMENTS 98
B SITE-MIXED CONCRETE FOR MINOR WORKS 102
C STORMWATER DRAINAGE INSTALLATION PLANS 103
D GUIDELINES FOR DETERMINING RAINFALL INTENSITIES 105
E RAINFALL INTENSITIES FOR AUSTRALIA— 5 MIN DURATION 106
AS/NZS 3500.3:2003
Page
F RAINFALL INTENSITIES FOR NEW ZEALAND ~ 10 MIN DURATION 124
G EXAMPLES OF OVERFLOW MEASURES FOR EAVES GUTTERS 129
H GENERAL METHOD FOR DESIGN OF EAVES GUTTER SYSTEMS —
EXAMPLE 133
I BOX GUTTER SYSTEMS — GENERAL METHOD, DESIGN GRAPHS AND
ILLUSTRATIONS 143
J BOXGUTTERSYSTEMS — GENERAL METHOD — EXAMPLES 152
K SURFACE DRAINAGE SYSTEMS —NOMINAL AND GENERAL
METHODS — EXAMPLES 162
L EXAMPLECALCULATION — PUMPED SYSTEM 173
M SUBSOILDRAINAGE SYSTEMS — DESIGN 175
AS/NZS 3500.3:2003
STANDARDS AUSTRALIA/STANDARDS NEW ZEALAND
Australian/New Zealand Standard
Plumbing and drainage
Part 3: Stormwater drainage
SEC T I ONI SCO P E AND G E N E R A L
1.1 SCOPE AND APPLICATION
1.1.1 Scope
This Standard covers materials, design, installation and testing of roof drainage systems,
surface drainage systems and subsoil drainage systems to a point of connection.
1.1.2 Application
1.1.2.1 Building Code of Australia
This Standard may be used as a means of demonstrating compliance with the requirements
of Part Fl of Volume One and Parts 3.1.2 and 3.5.2 of the Housing Provisions of the
Building Code of Australia.
This Standard will be referenced in the Building Code of Australia by way of BCA
Amendment 14 to be published by 1 May 2004.
1.1.2.2 Plumbing Code of Australia
This Standard will be referenced in the Plumbing Code of Australia.
1.2 REFERENCED DOCUMENTS
The documents referred to in this Standard are listed in Appendix A.
NOTE: A list of related documents is given in Paragraph A2, Appendix A
1.3 DEFINITIONS
1.3.1 General
For the purpose of this Standard, the definitions in AS/NZS 3500.0 and those below apply.
The definitions listed below specifically apply to this Standard,
1.3.2 Average recurrence interval (ARI)
The average or expected interval between events of a given rainfall intensity being
exceeded.
NOTE: The ART is an average value based on statistical analysis. The actual time between
exceedances will vary.
1.3.3 Box gutter
Graded channel, generally of rectangular shape, for the conveyance of rainwater, located
within the building. Includes a gutter adjacent to a wall or parapet (see Figures 15, 17).
1.3.4 External stormwater drainage network
A system that collects and conveys stormwater from individual properties.
NOTE: The network includes easement or inter-allotment drains, and street and trunk drainage
systems.
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AS/NZS 3500.3:2003
1.3.5 Inert catchment
A rainwater collection area whose dominant material has little or no effect on the chemical
composition of rainwater draining from it. Such materials include acrylic, fibreglass,
aluminium/zinc alloy-coated steel, glass, glazed tiles, unplasticized polyvinyl chloride and
pre-painted metal.
1.3.6 On-site stormwater detention (OSD)
A device for the temporary storage of stormwater, above or below ground, to reduce the
peak flow to the stormwater drainage network.
1.3.7 Overflow device
A device to safely divert flow in the event of a blockage, for use with the roof drainage
system of a box gutter.
1.3.8 Overflow measure
Measure to divert water from flowing back into a building from a blockage anywhere along
or at the outlet of an eaves gutter (see Figure Gl).
1.3.9 Permanent ponding
Ponding along the sole of eaves and box gutters when free water is evident for more than
three days after the cessation of flow.
1.3.10 Point of connection
The point provided for the connection of a site stormwater drain to the stormwater drainage
network.
NOTE: Where a property is more than 90 m from an external stormwater drainage network, the
network utility operator may permit an alternative point of connection.
1.3.11 Rainhead
A collector of rainwater, generally of rectangular shape, at the end of a box gutter and
external to a building, connected to an external downpipe (see Figure 12). it has a similar
function to a sump (see Clause 1 .3.19).
1.3.12 Sag pit
An inlet pit located in a depression where stormwater ponds over the inlet due to restricted
entry.
1.3.13 Spreader
A device fitted to the foot of a downpipe to evenly distribute rainwater onto a roof at a
lower level. It is generally used where it is undesirable for practical or aesthetic reasons to
connect the high-level roof downpipe directly to the storm water drainage system.
1.3.14 Stormwater
Naturally occurring water that results from rainfall on or around the site, or water flowing
onto the site.
1.3.15 Stormwater drainage system
The roof drainage system, surface drainage system and subsoil drainage system on a
property, which is used for the collection and conveyance of stormwater.
1.3.16 Subsoil drain
A buried conduit for the collection and conveyance of subsurface and ground water.
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9 AS/NZS 3500.3:2003
1.3.17 Sump
A collector of rainwater, generally of rectangular shape, in the sole of a box gutter and
connected to a downpipe within the building perimeter. Its function is to increase the head
of water at the entry to the downpipe and thus increase the capacity of the downpipe (see
Figures 15 and 17).
1.3.18 Sump/high capacity overflow device
An overflow device associated with an internal box gutter and sump (see Figure 3.7(c)).
1.3.19 Sump/side overflow device
An overflow device associated with an internal box gutter alongside a parapet wall (see
Figure 2.7(b)).
1.3.20 Valley gutters
Inclined channels placed at the intersecting sloping surfaces of the adjacent roof for the
conveyance of rainwater.
1.3.21 Plastics abbreviations
The following plastics abbreviations are used in this Standard.
PVC-U Unplasticized polyvinyl chloride
PVC-M Modified polyvinyl chloride
PVC-0 Oriented polyvinyl chloride
PE Polyethylene
PP Polypropylene
PE-X Cross-linked polyethylene
ABS Acrylonitrite styrene
PB Polybutylene
1.4 NOTATION
1.4.1 Quantity symbols
Quantity symbols used in this Standard are listed below.
Quantity
Symbol
Definition
A == cross-sectional area of flow in an open channel
Ac = catchment area of a roof and vertical surface (wall or
parapet)
^cdp = for a selected eaves gutter, the maximum catchment area of
roof per vertical dow npipe (see Appendix H)
v4s„e "^ eaves gutter sub-catchment area for a particular downpipe
and high point layout
Aq = effective cross-sectional area of a gutter
^h "^ plan area of a roof including the gutter or parapet which is
part of the catchment
y^hdp ^ for a selected eaves gutter, the maximum plan area of roof
per downpipe
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Unit
m^
m^
2
m
m^
mm^
m^
9
m~
AS/NZS 3500.3:2003 10
Quantity
Symbol
^T
Definition
v4|is.c = plan area of sub-catchment roof including the gutter or
parapet which is part of the catchment
A^ = total unroofed impervious (paved) catchment area
A^ =" total unroofed pervious catchment area
Ay = total roofed catchment area
A^ = maximum elevation area of a sloping roof, vertical surface,
wall or parapet
blockage factor, for inlet-to-inlet pit
Unit
m'
m^
m^
w'
m'
hn = nominal breadth of cross-section of a rectangular or square m m
down pipe
ZC// == equivalent impervious area of all upstream areas on the m"
property
Ci = run-off coefficient, for an unroofed impervious (paved) area —
Cp = run-off coefficient for an unroofed pervious area —
C, = run-off coefficient for a roofed area —
Dq = effective equivalent diameter of a rectangular mm
downpipe,
2^ |_n_^i_^ , or square downpipe 2^ -^
/3i = internal diameter of a circular downpipe mm
d\y^ ^ minimum depth of a box gutter that discharges to a mm
sump/high-capacity overflow device (includes h[) (see
Figure 3.10 and Figure 17)
dp = depth of ponding over an inlet to an inlet pit m
doc ^ minimum depth of an overflow channel mm
F =^ catchment area of a roof-slope factor (see Table 3.2) —
//,, = minimum depth of a box gutter that discharges to a mm
rainhead (includes /?r) (see Figure f I)
/?e = effective depth mm
hi = freeboard mm
hy = total depth of a rainhead mm
//^ = depth of a sump mm
/zt = minimum height of the top of the box gutter above the crest mm
of the overflow weir or channel as shown on Figures 15 and
17
^I\ ^ rainfall intensity for a duration of/ and an ARI of Y mm/h
k = Colebrook-White roughness coefficient mm
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AS/NZS 3500.3:2003
Quantity
Symbol
/r
m
n
P
R
S
Q
Qc
Q.
T
Woe
Y
Definition
for a sump/side overflow device, the minimum horizontal
distance between the sides of an overflow channel and
those of the sump (see Figure 15)
for sump/high-capacity overflow device, the height of
the overflow weir (crest) above the sole of the gutter
(see Figure 17)
length of a rainhead
multiplier for rainfall run-off coefficients (see
equation 3.4.6)
Manning roughness coefficient for an open channel
wetted perimeter of an open channel
hydraulic radius, R - /(^
gradient, for an open channel
design flow of stormwater
discharge capacity for an open channel
capacity of an inlet for a sag pit
time
width of a box gutter
effective width
nominal width of cross-section of a rectangular or square
downpipe
width of an overflow channel
average recurrence interval (ARI)
Unit
mm
mm
mm
m
m
L/s
L/s
min
mm
mm
mm
mm
years
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AS/INZS 3500.3:2003
12
1.4.2 Flow chart symbols
Flow chart symbols and conventions used in this Standard are listed below.
Flow chart symbol
Use
terminator, represents an entry from or an exit to an
outside environment, e.g., start or finish of a
flow chart
= data input
_ process, execute defined operation or group of
operations resulting in a change in value
decision or switching, a single entry with more than
one exit only one of which will be activated following
the evaluation of the condition
connector, represents an exit to or an entry either from
another part of the same flow chart, or from another
flow chart and corresponding symbols shall contain
the same unique identification
1.4.3 Gradients
In this Standard, gradients are expressed in the form of a numerical ratio Y:X, where Y is
the vertical dimension and X is the horizontal dimension of a right-angle triangle.
1.5 IDENTIFICATION
Where, other than in single dwellings, pipework that cannot be immediately and clearly
identified is installed in ducts, accessible ceilings or exposed in basements, plant rooms, or
similar, it shall be clearly identified in accordance with AS 1345 orNZS 5807.
1.6 PROTECTION OF WORKS
1 .6.1 Roof drainage systems
NOTE: Roof drainage systems that could be damaged by acid should not be installed adjacent to
or below brickwork prior to its having been washed down with acid or similar.
1.6.2 Surface drainage and subsoil drainage systems
Whenever the ground is opened for any purpose, within or in proximity to a property, all
necessary measures shall be taken to protect the surface drainage and subsoil drainage
systems from damage during the course of such work, and to prevent the entry of —
(a) soil, sand, or rock;
(b) sewage, including the contents of any septic tank, or trade waste; or
(c) any other substance that would damage or impede the operation of the stormwater
drainage network.
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AS/NZS 3500.3:2003
1.7 DISCHARGE POINT CRITERIA
1.7.1 Position and manner of discharge
NOTES:
1 The authority having jurisdiction may determine the position and manner of discharge of the
stormwater drainage system.
2 Point(s) of connection to the stormwater system for a property—
(a) may be located —
(i) within the property; or
(ii) external to the property, i.e., the surface water drain extends beyond the
property; and
(b) should transfer stormwater by gravity or pumping, or both, from the site stormwater
drain to the stormwater drainage network.
3 The forms of points of connection include —
(a) a direct connection to a street kerb and gutter (see Clause 8.6. 1 .2(c)); or
(b) connection to an element of the externa] stormwater drainage network, e.g. a conduit or
open channel located in a street or easement.
4 Where the stormwater from a property discharges through a mountable kerb to the gutter of a
roadway, the design and materials used to create the outfall should have sufficient strength
and durability to withstand the loads to which it will be subjected throughout the service life
of the kerb. The structural adequacy of the preformed outlets should be verified by load
testing or structural analysis. Any preformed outlet should be approved by the network utility
operator before being installed. Where practicable, for new kerb construction, outlets should
be installed in conjunction with the forming of the kerb.
5 Where the network utility operator has determined an operating water level, within its own
external stormwater drainage network for a gravitational point of connection, care should be
taken to ensure that any floor or basement level is above this level, and that the site
stormwater system has appropriate outlets to operate as surcharge outlets (see also
Clause 5.4.12).
6 Where the recommendations of Note 4 cannot be applied, consideration should be given to the
installation of —
(a) a reflux valve (see Clause 8.4); or
(b) a pumped system (see Section 9).
1.7.2 Stormwater drainage plans
NOTE: Typical information that may be required for a stormwater plan is given in Appendix C.
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AS/NZS 3500.3:2003 14
SECTION 2 MATERIALS AND PRODUCTS
2.1 SCOPE OF SECTION
This Section specifies requirements for materials and products for use in a stormwater
drainage system.
2.2 AUTHORIZATION
NOTE: In states and territories where stormwater installations are required to comply with the
Plumbing Code of Australia, materials and products used in stormwater and drainage systems
may require authorization and shall be manufactured to the relevant Australian Standard (see
PCA).
2.3 SELECTION AND USE
Materials and products used in a stormwater drainage system shall be selected to ensure
satisfactory service for the life of the installation.
Factors to be taken into account in the selection shall include but not be limited to—
(a) the nature of the intended use of the building:
(b) the environment;
NOTE: See AS/NZS 2312 or the relevant product Standard.
(c) the nature of the ground, quality of subsoil water and the possibility of chemical
attack there from;
(d) the physical (e.g., abrasion) and chemical (e.g., corrosion) characteristics of the
materials and products; and
(e) components of installations manufactured from more than one material, with either
contact between or drainage to them (see Note 3).
NOTES:
1 The manufacturer's recommended installation and maintenance procedures for the materials
and products selected should also be considered.
2 Where materials are used for collection of drinking water, the use of materials complying to
AS/NZS 4020 should be considered.
3 For material compliance see Clause 4.4. 1 or Clause 4.4.2.
2.4 ROOF DRAINAGE SYSTEM
2.4.1 Roof drainage system components
Roof drainage system components made from aluminium alloys, aluminium/zinc alloy-
coated steel, copper, copper alloys, zinc-coated steel, stainless steel and zinc shall comply
with AS/NZS 2179.1.
PVC components shall comply with AS/NZS 2179.2(lnt).
2.4.2 Downpipes
Materials and products, other than those specified in Clause 2.4.1, used for downpipes shall
comply with the following:
(a) AS/NZS 1866 for aluminium alloy pipes, which shall be in straight lengths, i.e., not
bent.
(b) AS 163 I for cast iron pipes and fittings.
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15 AS/^ZS 35003:2003
(c) AS 1432 and AS 3517, respectively, for copper pipes and fittings which shall satisfy
the following additional criteria:
(i) When Type B pipe is field bent, the offset angle shall be not greater than I 0°.
(ii) Type D pipe shall be in straight lengths, i.e. not bent.
(iii) Fabricated bends and junctions at the base of downpipes less than 9 m high
shall be, as a minimum, fittings suitable for Type D applications.
(d) Copper alloy pipes and fittings as specified in AS 3795 and AS 3517, respectively,
with the following limitations on use:
(i) Type D shall be in straight lengths, i.e., not bent.
(ii) Only junctions shall be field fabricated.
(iii) Only cast or hot-pressed bends and junctions shall be used at the base of
downpipes with heights equal to or greater than 9 m.
(e) Ductile iron pipes and fittings as specified in AS/NZS 2280.
(f) Fibre-reinforced concrete (FRC) pipes and fittings as specified in AS 4139, which
shall be autoclaved.
NOTE: Where FRC pipes are used in areas aggressive to concrete pipes the manufacturers
recommendations should be sought.
(g) Galvanized steel pipes and malleable cast iron fittings as specified in AS 1074 and
AS 3673, respectively, with the following limitations on use:
(i) Pipes shall be in straight lengths, i.e., not bent.
(ii) Pipes and fittings shall be installed in accessible locations,
(h) Glass-filament-reinforced thermosetting plastics (GRP) pipes as specified in
AS 3571, and where exposed to direct sunlight, have adequate resistance to UV.
(i) Polyvinyl chloride (PVC) pipes and fittings as specified in AS/NZS 1254,
AS/NZS 1260, AS 1273, AS/NZS 1477 or AS/NZS 2179.2(lnt).
0) Polyethylene (PE) pipes and fittings complying with AS/NZS 4 129, AS/NZS 4 130 or
AS/NZS 4401 (Int), and unless coloured black, pipes and fittings shall not be exposed
to direct sunlight without protection in accordance with AS 2033.
2.4.3 Accessories and fasteners
Accessories and fasteners manufactured from aluminium alloys, aluminium/zinc alloy-
coated steel, copper, copper alloys, zinc-coated steel, stainless steel and zinc shall comply
with AS/NZS 2179,1.
NOTES:
1 Metal accessories and fasteners specified in AS/NZS 2179.1 may be suitable for gutters and
downpipes manufactured from PVC.
2 Accessories manufactured from PVC should comply with AS/NZS 2]79.2(lnt).
2.5 STORMWATER DRAINS (NON-PRESSURE)
The following applies to products used for non-pressure stormwater drains:
(a) Aluminized or galvanized steel shall be as specified in AS 1761 .
(b) Cast iron, copper, copper alloys, ductile iron pipes and fittings shall comply with
Items (b) to (e), respectively, of Clause 2.4.2.
(c) FRC pipes and fittings shall be as specified in AS 4139 and shall have the following
limitations on use:
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AS/NZS 3500.3:2003 16
(i) Site fittings shall be concrete encased where the resin used to manufacture
fittings has not been designed for the required stormwater drainage in-service
application.
NOTE: Where FRC pipes are used in areas aggressive to concrete pipes the
manufacturer's recommendations should be sought.
(ii) Pipes and fittings shall be autoclaved.
(d) Galvanized steel pipes and malleable cast iron shall comply with Clause 2.4.2 (g).
(e) GRP pipes and fittings, minimum Class SN 2500, shall be as specified in AS 3571
and shall, where exposed to direct sunlight, have adequate resistance to UV radiation.
(f) PE pipes shall comply with Clause 2.4.2(j).
(g) Precast concrete pipes (steel reinforced) as specified in AS 4058 or NZS 3107 and,
where located under buildings, they shall have no lifting holes.
MOTE: Where concrete pipes are used in areas aggressive to concrete pipes the
manufacturer's recommendations should be sought.
(h) Circular PVC pipes and fittings shall comply with Clause 2.4.2(1).
(i) Stainless steel shall be as specified in Section 2 of AS/NZS 3500.1 .
(j) Vitrified clay or ceramic pipes and fittings shall be as specified in BS EN 295-1 .
2.6 RISING MAINS (PRESSURE)
Rising mains shall be constructed from pressure pipes and fittings as specified in Section 2
of AS/NZS 3500.1.
2.7 SUBSOIL DRAINS
Plastics pipes used in subsoil drains shall comply with AS 2439.1. Class 100 of such pipes
shall be limited to use in single dwellings.
2.8 JOINTS
2.8.1 Resin adhesives
2.8.1.1 General
Resin adhesives shall have positive adhesion to, and compatibility with, the materials being
jointed.
2.8.1.2 Sealants
Sealants, including caulking compounds and tapes, shall —
(a) be neutral cure;
(b) where exposed above ground, be resistant to ultraviolet radiation;
(c) have the appropriate range of service temperatures for the location;
(d) have positive adhesion to and compatibility with the materials being jointed; and
(e) where applicable, retain flexibility throughout the service life.
2.8.1.3 Silver brazing alloy
Silver brazing alloys used for jointing copper and copper alloy pipes and fittings shall
comply with AS I 167.1 and shall have a silver content of not less than 1 .8%.
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2.8.1.4 Soft solder
Soft solder shall comply with AS 1834.1 and —
(a) for roof drainage system components, used for the conveyance of drinking water,
have a lead content of not more than 0. 1 %;
(b) for zinc-coated steel, copper, copper alloy and stainless steel, be 50/50 solder to
Grade 50 Sn; and
(c) for zinc, have an antimony content of less than 0.5%.
2.8.1.5 Solvenl cement and priming fluid
Solvent cement and priming fluid used for jointing PVC pipes and fittings shall comply
with AS/NZS 3879.
2.8.2 Types
2.8.2.1 Bol/ed gland (EG)
Bolted gland joints shall comply with AS 1631 for cast grey and ductile iron materials with
elastomeric seals appropriate to the material and dimensions of the pipes or fittings being
jointed,
2.8.2.2 Cement mortar (CM)
Cement mortarjoints shall comply with Clause 2.10.4,
2.8.2.3 Elastomeric seals (ES)
Elastomeric seals shall comply with the relevant product Standard.
2.8.2.4 Epoxy resin (ER)
Epoxy resin shall be appropriate to the materials being jointed and shall be mixed and
applied in accordance with the manufacturer's instructions. Epoxy resin shall be used only
where the joint is designed for its use.
Fittings fabricated on site using an epoxy should be concrete encased when installed below
a permanent water table unless the epoxy has been approved for use in such applications.
2.8.2.5 Fusion welded (FW)
Fusion welded joints shall be appropriate to the materials being jointed and carried out with
suitable consumables and techniques in accordance with the manufacturer's
recommendations by a suitably qualified competent person.
2.8.2.6 Mechanical coupling (MC)
Mechanical couplings shall comply with AS 1 761 .
2.8.2.7 Metal-banded flexible coupling (FC)
Metal-banded flexible couplings shall comply with AS/NZS 4327.
2.8.2.8 Silver brazed (SB)
Silver-brazed joints shall be made from silver brazing alloy complying with Clause 2.8. 1 .3.
Joints shall be made by either —
(a) using authorized fittings; or
(b) fabricating junctions from the pipes.
2.8.2.9 Soft soldered (SS)
Soft soldered joints shall be made from solder complying with Clause 2.8.1.4 and shall be
used only for jointing zinc-coated steel, copper, copper alloy and stainless steel rainwater
goods.
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AS/N/.S 3500.3:2003
2.8.2.10 Solvent cement (SC)
Solvent cement joints for PVC pipes and fittings shall be made in accordance with
AS 2032.
2.8.2.11 Threaded (TH)
Threaded joints shall comply with the relevant standards for the materials to be jointed and
be sealed with an appropriate jointing medium.
2.9 VALVES
2.9.1 Gate and globe
Copper alloy gate and globe valves shall comply with AS 1628.
2.9.2 Flap
Flap valves shall comply with Clause 2.3.
2.9.3 Non-return
Cast iron and copper alloy non-return valves shall comply with AS 3578 and AS 1628,
respectively.
2.9.4 Reflux
Reflux valves shall comply with Clause 2.3.
2.9.5 Sluice
Gate valves shall comply with AS 2638.1 or AS 2638.2.
2.9.6 Wedge gate
Cast iron wedge gate valves shall comply with AS 3579.
2.10 CONCRETE AND MORTAR
2.10.1 Concrete
Ready-mixed concrete shall comply with AS 1379 and shall have a minimum characteristic
compressive strength of 1 5 MPa, as defined in AS 3600.
For minor works, site-mixed concrete shall consist of cement, fine aggregate, and coarse
aggregate all measured by volume, and sufficient water added to make the mix workable. It
shall have a minimum strength compromise of 15 MPa.
NOTE: See Appendix B for typical mixes for minor works.
Packaged concrete mixes shall comply with AS 3648.
2.10.2 Cement mortar
Cement mortar shall consist of one part cement and three parts fine aggregate measured by
volume, thoroughly mixed with the minimum amount of water necessary to render the mix
workable.
Cement mortar, which has been mixed and left standing for more than I h, shall not be
used.
2.10.3 Chemical admixtures
Chemical admixtures used in concrete shall comply with AS 1478.1.
2.10.4 Water for concrete and mortar
Water used for mixing concrete and cement mortar shall be free from matter that is harmful
to the mixture, the reinforcement or any other items embedded within the concrete or
mortar.
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19 AS/NZS 3500.3:2003
2.10.5 Steel reinforcement
Steel reinforcing materials used in concrete structures shall comply with AS/NZS 4671.
2.11 EMBEDMENT MATERIAL
2.11.1 Site stormwater drains
Embedment material for below ground site stormwater drains shall be as specified in
Clause 7.4.2.1.
2.11.2 Subsoil drains
Embedment for subsoil drains shall be as specified in Clause 7.4.2.1 .
2.12 trench: FILL
Trench fill for site stormwater drains and subsoil drains shall be as specified in
Clause 7.2.12.
2.13 MISCELLANEOUS
2.13.1 Clay building bricks
Clay building bricks shall comply with AS/NZS 4455.
2.13.2 Concrete masonry units
Concrete masonry units (concrete bricks or concrete blocks) shall comply with
AS/NZS 4455.
2.13.3 Cover and sump grates
Metal access cover and sump grates and frames for stormwater and inlet pits and arresters
shall comply with AS 3996. Structurally adequate support shall be provided for access
covers, sump grates and frames.
2.13.4 External protective coating
The external protective coating of metal pipes and fittings shall —
(a) be impervious to the passage of moisture;
(b) be resistant to —
(i) the external corrosive environment; and
(ii) damage by the embedment material; and
(c) not contain material that could cause corrosion.
2.13.5 Fibregfass-reinforced plastic tanks
Water collection tanks for re-use water shall comply with AS/NZS 3500.1
2.13.6 Geotextiles
Geotextiles shall be marked in accordance with AS 3705 and shall comply with Clause 2.3.
2.13.7 Polyethylene sleeving
Polyethylene sleeving for corrosion protection shall comply with AS 3680.
2.13.8 Precast or prefabricated pits and arresters
2.13.8.1 Concrete
Precast concrete units for pits shall comply with the dimensions given in Table 8.2, and
shall—
(a) in ISew Zealand, comply with all relevant requirements of NZS 3 107;
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AS/NZS 3500.3:2003 20
(b) comply with the relevant criteria of AS 41 98; or
(i) support for a minimum of 30 s, without structural failure or significant
cracking, the appropriate pit lid design loads in accordance with AS 3996
(where a precast unit has knock-out panels, this requirement shall apply with
the knock-out panels removed); and
(ii) be classified and marked in accordance with the pit lid classification of
AS 3996 for which they are designed.
2.13.8.2 Corrugated metal
Prefabricated corrugated metal pits and arresters shall comply with AS 1761 and shall
support, without structural failure, the appropriate pit lid design loads in accordance with
AS3996.
2.13.8.3 Other materials
Precast or prefabricated pits and arresters of materials, other than specified in
Clauses 2.13.8.1 and 2.13.8.2, shall satisfy the performance requirements of the Plumbing
Code of Australia and shall support, without structural failure, the appropriate pit lid design
loads in accordance with AS 3996.
2.13.9 Timber
Timber exposed to the weather shall be of durability Class 2 complying with AS/NZS 2878
or NZS 363 1 or shall be treated in accordance with AS 1604.1 or NZS 3640.
2.14 FILTERS FOR SUBSOIL DRAINS
2.14.1 Filter material
Filter materials consisting of natural clean washed sands and gravels and screened crushed
rock shall be —
(a) well graded, with a mix of different sizes of sand particles and an adequate
permeability with —
(i) natural sand, less than 5% passing a 75 jum sieve; and
(ii) screened crushed rock, sizes 3 mm to 20 mm;
(b) sufficiently coarse not to wash into the subsoil drain, or through pores in a geotextile
cover to such drain; and
(c) chemically stable and inert to possible actions of soil and ground water.
NOTE: Design requirements set on the basis of the grading curves of the native soils and
filter material are too complex for routine use by builders, and require specific tests.
2.14.2 Geotextile filters
The permeability of geotextiles used in subsoil drains shall be greater than that of the native
soil.
NOTES:
1 A desirable permeability for geotextiles is 10 times that of the native soil.
2 There is a tendency for geotextiles to clog at some locations, particularly where iron salts are
present, e.g., scoria. Oxidization and biologically related actions can cause plate-like deposits
of ferruginous particles on filter surfaces, rapidly clogging them. In such areas, carefully
selected granular filters should be used instead of geotextiles. Advice from a professional
engineer with geotechnical expertise should be sought in such situations.
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SECTION 3 ROOF DRAINAGE SYSTEMS^
D E SIGN
3.1 SCOPE OF SECTION
This Section specifies methods for the design of and procedures for roof drainage systems.
3.2 GENERAL METHOD
The general method assumes regular inspection and cleaning (see Clause 4.6) and is
applicable to —
(a) eaves gutters and associated vertical downpipes with appropriate overflow measures
(see Clause 3.5);
(b) valley gutters (see Clause 3.6);
(c) box gutters and associated vertical downpipes with appropriate overflow devices (see
Clause 3.7); and
(d) soakers (see Clause 3.8).
NOTES:
1 The general method does not include allowance for any of the following:
(a) Localized variation in rainfall intensities due to wind or adjacent buildings.
(b) Blockages of roof drainage systems, e.g., by snow, hail and debris.
(c) Reduced hydraulic capacity caused by—
(i) reduced gutter gradient due to ground movement; or
(ii) turbulence due to wind.
2 An example that illustrates the application of the general method is given in Appendix H.
3.3 METEOROLOGICAL CRITERIA
3.3.1 General
Roof drainage systems are designed in respect to potential monetary loss, property damage
(including contents of buildings) and injury to persons due to overtopping.
NOTES:
1 A frequent cause of such overtopping is inadequate inspection and cleaning (see Clause 4.6)
and not the intensity of rainfall.
2 Although hail can restrict or block roof drainage systems the present lack of performance data
prevents the inclusion of requirements for hail barriers, as published in REBUILD (see Ref 8,
Paragraph A2, Appendix A).
3.3.2 Snowfall effects
In regions subject to snowfalls, for roof drainage systems, there shall be no effect on size
but precautions are necessary to minimize the entry of rainwater or meltwater, or both, into
buildings.
NOTES:
1 Roof drainage support systems should be designed to include an appropriate allowance for
snow toad (see AS/NZS 1 170.3).
2 Sometimes eaves gutters are not used in alpine regions because the stormwater from roofs is
collected at ground level, generally in site stormwater channels.
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3.3.3 Wind effects
An allowance for the effects of wind on rainfall is required for other than flat or
permanently protected sloping surfaces (see Clause 3.4). A gradient of 2:1 shall be adopted.
NOTE: As studies in Australia are insufficient to determine the maximum gradient of descent of
wind-driven rain at design intensity United Kingdom practice has been adopted (see
BS EN 12056-3)
3.3.4 ARI
The ARI shall be as given in Table 3.1.
TABLE 3.1
AVERAGE RECURRENCE INTERVAL (ARI)
Effect of overtopping
ARI, years
Australia
New Zealand
Where significanL inconvenience or
injury to people or damage to
property (including contents of
buildings) is —
(a) an unlikely oceurrenee, e.g.,
eaves gutters, external; or
(b) a likely occurrence, e.g., box
gutters
>20
>100
>I0
>50
NOTE; For Australia Table 3.1 should be used in conjunction with the
BCA, which has requirements to prevent rain and stormwater from roof
drainage from entering certain buildings.
3.3.5 Rainfall intensity
3.3.5.1 Alls Ir alia
Five minutes duration rainfall intensity, in millimetres per hour, for any place in Australia
shall be determined for —
(a) ARIs of 20 and 1 00 years, from Appendix E; and
(b) ARI of 500 years, assumed to be 1.5 times the 100 years ARI intensity at the same
place.
NOTE: Guidelines for the determination of rainfall intensity are given in Appendix D.
3.3.5.2 New Zealand
Ten minutes duration rainfall intensity, in millimetres per hour, for any place in
New Zealand shall be determined for ARIs of 1 and 50 years, from Appendix F.
NOTE: Guidelines for the determination of rainfall intensity are given in Appendix D.
3.4 CATCHMENT AREA
3.4.1 General
The catchment area for a roof, or roof and vertical wall(s), depends upon the gradient of the
descent of the rain (see Clause 3.3.3) and shall be the greatest value for any direction of
wind-driven rain.
>JOTE: It may be necessary to trial different directions for the wind-driven rain to determine the
catchment area for a particular case.
The components of the largest catchment area for a single dwelling (see Paragraph H2,
Appendix Tl) shall be calculated by one of the following methods:
(a) Rational analysis.
(b) Application of Clauses 3.4.2 to 3.4.4, inclusive.
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3.4.2 Three-dimensional representation
A three-dimensional representation of the two components Au and A^ of the catchment area
for a sloping roof with its top edge either horizontal or not horizontal is shown in
Figure 3.1. These components are represented in Figures 3.2 and 3.3 by lines in the
horizontal and vertical planes.
3.4.3 Roof
The catchment area, in square metres, of —
(a) a flat roof that is freely exposed to the wind shall be equal to the plan area of the roof
and gutter(s);
(b) a single sloping roof that is —
(i) freely exposed to the wind (see Figure 3.3(a)) shall be calculated from —
4-A+l/2 4.or, ...3.4.3(1)
for eaves gutters only
A,^A,F ...3.4.3(2)
(For values of F, see Table 3.2.)
NOTE: F is accurate in most cases and conservative in others.
(ii) partially exposed to the wind (see Figure 3.3(b)) shall be calculated from —
^, = A +1/2(^2 -^vi) ...3.4.3(3)
(c) two adjacent sloping roofs (see Figure 3.3(c)) shall be calculated from —
A = Ai + A2 + 1/2 (A2 - Ai) • • • 3.4.3(4)
NOTE: Equation 3.4,3(2) may be applied to the plan area of a roof (A],) of a dwelling regardless
of the wind direction provided that there is no vertical surface that contributes to the catchment
area (see Appendix H).
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TABLE 3.2
CATCHMENT AREA— SLOPE FACTOR (F) (FOR EAVES GUTTERS ONLY)
Roof slope
(degrees)
Factor for
increased
surface area of
roof (F)
Roof slope
(degrees)
Factor for
increased
surface area of
roof (F)
Roof slope
(degrees)
Factor for
increased
surface area of
roof (F)
1.00
22
1.20
44
1.48
1
l.Ot
23
1.21
45
1.50
2
1.02
24
1.22
46
1.52
3
1.03
25
1.23
47
1.54
4
1.03
26
1.24
48
1.56
5
1.04
27
1.25
49
1.58
6
1.05
28
1.27
50
1.60
7
1.06
29
1.28
51
1.62
8
1.07
30
1.29
52
1.64
9
1.08
31
1.30
53
1.66
10
1.09
32
1.31
54
1.69
1 1
1.10
33
1.32
55
1.71
12
l.ll
34
1.34
56
1.74
13
1.12
35
1.35
57
1.77
14
1.12
36
1.36
58
1.80
15
1.13
37
1.38
59
1.83
16
1.14
38
1.39
60
1.87
17
1.15
39
1.40
61
1.90
18
1.16
40
1.42
62
1.94
19
1.17
41
1.43
63
1 .98
20
1.18
42
1.45
64
2.03
21
1.19
43
1.47
65
2.07
Roof
surface
/—Top edge of roof
horizontal
Roof
surface-
\ Vertical plane
Horizontal plane
Roof angle
(a) Top edge of roof
horizontal
Top edge of roof
NOT horizontal
-Vertical plane
Horizontal plane
Roof angle
(b) Top edge of roof
not horizontal
FIGURE 3.1 COMPONENTS OF THE CATCHMENT AREA
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AS/NZS 3500.3:2003
\ \ \ \ \ \ \ \ \ \ \ \ \^~f
\\\\\\\2h\\\\^
\ \ \ \ \ \ \L\ \ \ \ \ \ '
\\\\\\\^\\\\\^ ^v
\\\\\\\\\\\\
\ \ \ \ \ \ \ \ \ \ \ \ V
^ \ \ \ \ ^
n !
(a) Vertical wall with
flat roof
(b) Vertical wall with
sloping roof
[c) Vertical walls at right angles to each other
FIGURE 3.2 CATCHMENTAREAFOR VERTICAL WALL(S) AND ROOF
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1/2A,
(a) Single sloping roof — freely exposed to the wind
r
i
\2
(b) Single sloping roof — partially exposed to the wind
Angle of descent
of rain-— ,^
\
\ \ \ \
\ \ \ \ \
. LA \ \ \
"^"\ \ ^ \ '\ '^ \ \ \
V \ \ \ \ \ \
(c) Two adjacent sloping roofs
FIGURE 3.3 CATCHMENT AREA FOR ROOFS
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3.4.4 Vertical wall(s) and roof
The catchment area, in square metres, for —
(a) vertical wall with a —
(i) flat roof (see Figure 3, 2(a)) shall be calculated from —
A^ = A,+\/2A^ ...3.4.4(1)
(ii) sloping roof (see Figure 3.2(b)) shall be calculated from —
^, = 4,+l/2(/(,2-/(„) ...3.4.4(2)
(b) vertical walls at right angles to each other (see Figure 3.2(c)) shall be calculated
from —
^, = A +1/2^1 + ^2) ...3.4.4(3)
NOTE; The catchment area for high vertical walls, e.g., a multistorey building, may be
considerably less than half its surface area.
3.4.5 Higher catchment area
Stormwater from a higher catchment area shall be discharged direct to an appropriately
sized rainhead or sump.
Alternatively a spreader, may be used subject to the following:
(a) For a tiled roof the lower section shall be sarked a minimum width of 1800 mm,
either side from the point of discharge, and extended down to the eaves gutter in
accordance with AS 2050.
(b) For a corrugated metal roof a minimum width of 1 800 mm on either side of the point of
discharge shall be sealed for full length of side laps.
In all cases the downpipe and gutter system of the lower catchment shall be sized in
accordance with Clause 3.4 to take into account the total flow from both catchments.
NOTES:
1 The rainhead or sump may need to be larger than those sized in accordance with this Standard
and include an appropriate device to dissipate energy. Sizing of such a rainhead or sump is
beyond the scope of this Standard and may require hydraulic tests.
2 Where spreaders are used, an allowance for an increased overflow provision for the gutter on
the lower catchment should be considered.
3 For a tiled roof consideration should be given to sarking the roof below any upper eaves
gutters to take into account any overflows.
3.5 EAVES GUTTER SYSTEMS
3.5.1 General
Eaves gutter systems, including downpipes, shall be designed and installed in accordance
with Clause 3.2 so that water will not flow back into the building.
3.5.2 Design procedure
The design procedure shall follow the general method for design of eaves gutters systems
flow chart, in Figure 3.4.
NOTE: An example of the application of the design procedure is given in Appendix H.
3.5.3 Overflow measures
Note: Examples of overflow measures for eaves gutters are given in Appendix G.
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3.5.4 Vertical downpipes
Gutter outlets shall be fitted vertically to the sole of eaves gutters.
f START J
-^
Determine the ARI from Clause 3.3.4 (Table 3,1).
For convenience this flow chart assumes that ARI of
20 years for Australia and 10 years for New Zealand are selected.
If other ARI are selected, adjust the flow chart to suit.
Determine the rainfall intensity for the site from Clause 3.3.5.
For Australia, see Appendix E Figures - Rainfall intensities i^^If^^] for 5 min
duration and an ARI of 20 years. (Referred to as 20/^},
For New Zealand, see Appendix F figures and determine ""-'/iq.
See Appendix D for guidelines for rainfall intensities.
^^
(c) / Obtain dimensions and other relevant data from physical observations and
measurements, plans or both. (See Appendix H for an example.)
Calculate catchment areas /Ih and /Ic in accordance with Clause 3.4.
Jl.
Select gradients in accordance with Clause 4.8
J^
(f)
(g)
Select eaves gutter from manufacturers date and note Aq values for gutter.
_^
Determine, for the affected eaves gutter, the catchment area per downpipe
Calculate minimum number of downpipes
Select downpipe locations and gutter high points, then calculate
catchment area for each downpipe
Review
selections
at
(e), (f)
(g), (h) an
d
(i). (See
Appendix
H
for
guidance]
(k) Determine downpipe size from Table 3.2 based on gradient and size of eaves gutter
Select over flow measures in accordance with clause 3,5
f FINISH J
FIGURE 3.4 (in part) FLOW CHART— GENERAL METHOD FOR DESIGN OF EAVES-
GUTTER SYSTEMS
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AS/NZS 35(M).3:2003
Al
NOTES:
1 The letter in a bracket at the head of each symbol refers to the corresponding step in the
example (see Paragraph H2.2, Appendix H).
2 Appendix D gives guidelines for the determination of rainfall intensities.
3 A^, to be in the range for gradients of —
(a) 1 :500 and steeper, 3000 mm^ to 1 8 000 mm"; or
(b) flatter than 1 :500, 4000 mm^ to 24 200 mm^
4 Consideration needs to be given to the criteria for thermal variation (see Clause 4.3).
5 For eaves gutters of domestic buildings with hipped and/or gable roofs of constant slope with
no flat roofs or walls contributing to the catchment area, the catchment area calculations may
be based entirely on Equation 3.4,3 (2) using F determined by the roof slope and A],
determined from a plan, if Equation 3.4.3 (2) is used, it is not necessary to take account of
wind direction. Examples of the use of this method are shown in Appendix H and in HBJ 14.
6 The vertical downpipe and any horizontal bends in an eaves gutter may be located at any
point along the length of the catchment. Where this occurs, the whole catchment to that
downpipe shall be used with Figure 3.5a or Figure 3.5b (gutters less than 1:500) to size the
eaves gutter to ensure that the vertical downpipe size is sufficient.
7 As there are no high points for flat eaves gutters to define the catchment areas for each
downpipe and downpipe section, halve the total catchment area between the adjacent
downpipes.
8 For aesthetic and practical considerations, the size of eaves gutter and associated vertical
downpipes for the largest catchment area of the building are usually adopted for each of the
other catchments.
FIGURE 3.4 (in part) FLOW CHART— GENERAL METHOD FOR DESIGN OF EAVES
GUTTER SYSTEMS
TABLE 3.3
EAVES GUTTER— REQUIRED SIZE OF VERTICAL DOWNPIPE
Maximum effective cross-sectional area of an
eaves gutter (A,), see AS/NZS 2179.1.
Internal size of vertical downpipe
(Required effective cross-sectional area is
obtained from Figure 3.5)
mm
Nearest 100 mm^
Gradient
Cross-
section
1:500 and steeper
Flatter than 1:500
Circular
Rectangular or square
3 500
4 700
65
65 X 50
4 200
5 600
75
65 X 50
4 600
6 200
75
75 X 50
4 800
6 400
80
75 X 50
5 200
7 000
80
lOOx 50
5 900
7 900
85
100 x50
6 400
8 600
90
100 x50
6 600
8 900
90
75 X 70
6 700
9 000
100
75 X 70
8 200
1 1 000
100
100x75
9 600
1 2 900
125
100 x75
12 800
17 100
125
100 X 100
12 800
17 200
150
100 X 100
16 000
21 500
150
125 X 100
1 8 400
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COPYRIGHT
AS/NZS 3500.3:2003
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* Sec AS/NZS 2179.1.
NOTBS:
1 This graph assumes —
(a) an clTeetive width to depth is a ratio of about 2:1;
(b) a gradient in the direction of ilow, 1 ;500 or steeper;
(c) the least favourable positioning of the downpipe and bends within the gutter length;
(d) a cross-section or half round, quad, ogee or square; and
(e) the outlet to a vertical downpipe is located centrally in the sole of the eaves gutter.
2 The required eaves gutter discharge areas do not allow for loss of waterway due to internal brackets.
FIGURE 3.5(A) REQUIRED SIZE OF EAVES GLITTERS FOR GRADIENTS FOR 1:500
AND STEEPER
COPYRIGHT
AS/NZS 3500.3:2003
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FOR GRADIENTS FLATTER THAN 1 : 500
^1 f 1 1 1 1 1 ! 1 1 1 1 1 1 1 1 1 1 1 [ 1
0.68 1.0
2.0
3.0
4.0
5.0
6.0
TOTAL FLOW IN EAVES GUTTER (L/s)
* See AS/NZS 2 1 79. 1.
NOTES:
1 This graph assumes —
(a) an elTeclive width to depth is a ratio of about 2:1;
(b) a gradient in the direction of How flatter than 1:500;
(e) the least favourable positioning of the downpipe and bends within the gutter length;
(d) a cross-section or half round, quad, ogee or square; and
(e) the outlet to a vertical downpipe is located centrally in the sole of the eaves gutter.
2 1'he required eaves gutter discharge areas do not allow for loss of waterway due to internal brackets.
FIGURE 3.5(B) REQUIRED SIZE OF EAVES GUTTERS FOR GRADIENTS FLATTER
THAN 1:500
COPYRIGHT
AS/NZS 3500.3:2003
3.5.5 Effective cross-sectional area of eaves gutters
The effective cross-sectional area of an eaves gutter (to the nearest 100 mm^) for each
nominal size of eaves gutter shall be as follows:
(a) For an eaves gutter with external brackets, it is the cross-sectional area beneath a line
not less than 10 mm below the overflow, e.g., front bead, gutter back or bottom of
overflow slots; or
(b) For an eaves gutter with internal brackets, it is as for Figure 3.5(A) or 3.5(B) less the
allowance for the effects of the brackets.
NOTES:
1 The cross-sectional area of the eaves gutter and the effect of internal brackets should be
available from the manufacturer.
2 The method specified in this Standard for the sizing of eaves gutters is based on research
using eaves gutters with external brackets.
3 Internal brackets increase the potential for debris collection.
4 Where the manufacture does not provide data on the effect of the internal bracket, the
projected gross area of the edge of the internal bracket including stiffening rib facing the
direction of ilow may be deducted, provided that the area so deducted is no more than 15% of
the original cross sectional area of the gutter.
3.6 VALLEY GUTTERS
3.6.1 Limitations
The limitations of the general method's solutions for valley gutters are —
(a) roof slopes of not less than 1:4.5 (12.5°);
(b) nominal valley gutter side angle (see Figure 3.6) of 1:3.4 (16.5°); and
(c) catchment area not exceeding 20 m .
3.6.2 Design procedure
The method of design for valley gutters shall be as follows:
(a) Select from Table 3.1 the ARI for the particular application.
(b) Determine the design rainfall intensity, in millimetres per hour, for the particular
location in Australia, from Appendix E or New Zealand from Appendix F for the
selected ART
NOTE: Appendix D gives guidelines for the determination of rainfall intensities.
(c) The girth size and dimensions (see Figure 3.6) shall be as given in Table 3.4 for the
design rainfall intensity.
NOTE: Table 3.4 is derived from the Martin and Tiiley Report (see Paragraph A2,
Appendix A). Further research when completed will be considered for adoption in the
Standard.
3.6.3 Effective width
The effective width (w^) of a valley gutter shall be such that the effective cross-sectional
area of valley gutters, below the effective width (see Figure 3.6), are not obstructed by
bedding, anti-vermin strips, or overhangs of roof cladding.
COPYRIGHT
33
AS/NZS 3500.3:2003
FIGURE 3.6 PROFILE OF A VALLEY GUTTER
TABLE 3.4
VALLEY GUTTERS— DIMENSIONS
Design rainfall intensity
Minimum, mm
(see Clause 3.6.2 (b))
mm/h
Sheet width
Effective
depth (Ae)
Effective
width (Wf.)
>200
>25()
>300
>350
<200
<250
<300
<350
<40()
355
375
395
415
435
32
35
38
40
43
215
234
254
273
292
NOTES:
1 Freeboard (//f), 15 inm.
2 The sheet width from which the valley is to be formed has been calculated on the
basis of hf= 15 mm and an allowance for side rolls or bends of 25 mm.
3.7 BOX GUTTER SYSTEMS
3.7.1 General
The limitation of solutions for —
(a) box gutters, is gradients in the range 1:40 to 1:200 (see Note 1);
(b) rainheads is —
(i) design flows not to exceed 16 L/s;
(ii) size range of vertical downpipes according to Figure 13, Appendix I; and
(c) sumps with appropriate overflow devices, is the size range of vertical downpipes
according to Figure 14, Appendix I.
NOTES:
1 Figures 16 and 18, Appendix I, assume that box gutters slope in the range 1 :40 to 1 :200.
2 Criteria for box gutter overflow devices are given in Clause 3.7.5 and are illustrated in
Figure 3.7.
3 The minimum width of box gutters used for commercial construction is 300 mm. Box gutters
200 mm wide may be used for domestic construction, but they are more prone to blockages
and should be subject to frequent inspections and maintenance. Additional height is
recommended where possible.
COPYRIGHT
AS/NZS 3500.3:2003 34
3.7.2 Design procedure
Box gutter systems shall be designed in accordance with the general method. The general
method for —
(a) box gutters, rainheads and downpipes is given in Figure 3.8.
(b) box gutters, sump/side overflow devices and downpipes is given in Figure 3.9.
(c) box gutters, sump/high-capacity overflow devices and downpipes is given in
Figure 3.10.
NOTE: Flow chart symbols and conventions used in this Standard are given in Clause 1.4.2.
3.7.3 Hydraulic capacity
The hydraulic capacity, e.g., maximum design flow of —
(a) a box gutter is dependent on —
(i) the sole width and gutter depth;
(ii) the gradient (see Clause 4.9(a)); and
(iii) whether the discharge is to —
(A) a rainhead;
(B) a sump/side overflow device; or
(C) a sump/high-capacity overflow device; and
(b) an associated rainhead or sump is dependent on the selected size of the vertical
downpipe and the deptb of the rainhead or sump (see Figures 3.9, 3.10 and 3.1 1).
NOTE: For the same design flow, the required depth of a rainhead or sump increases if the cross-
sectional area of the vertical downpipe decreases.
3.7.4 Layout
The layout for box gutter systems shall include consideration for the following:
(a) The location and size (see Clause 3.7.2) of the box gutter.
(b) The size (see Clause 4. 1 6) of the support system.
(c) Adequate provision for the effects of thermal variation (see Clause 4.3) on the box
gutter and support system.
(d) The location of associated vertical downpipes with rainheads or sumps in relation
to—
(i) features within the building and usage;
(ii) surface water drainage system external to the building (see Clause 5.3);
(iii) the space within or external to the building; and
(iv) provision for flow from each overflow device (see Clause 3.7.5) to be
discharged, without danger, indirectly to the surface water drainage system.
(e) The sump/high capacity overflow device — the depth of the sump h^ shall be not less
than 150 mm regardless of the position of the normal outlet. (Mo changes if sump/side
overflow device used).
(f) The normal outlet may be moved longitudinally to clear the overflow channel to
enable better inspection and maintenance access. The outlet shall not be moved
laterally to cross the longitudinal centre-line of the overflow device.
NOTE: If the normal outlet is moved, it should preferably be moved towards the box gutter
with the greater flow.
COPYRIGHT
35 AS/N/.S 3500.3:2003
(g) Box gutters shall —
(i) be straight (without change in direction);
(ii) in a cross-section have a horizontal constant width base (sole) with vertical
sides;
(iii) have a constant longitudinal slope between 1 :200 and 1 :40;
(iv) discharge at the downstream end without change of direction (i.e., not to the
side); and
(v) be sealed to the rainheads and sumps.
3.7.5 Overflow devices
3.7.5.1 Hydraulic capacity
The hydraulic capacity of an overflow device shall be not less than the design flow for the
associated gutter outlet. Overflow devices shall discharge to the atmosphere.
3.7.5.2 Operation
Overflow devices that discharge from —
(a) rainheads do not require an increase in the depth of flow in the box gutter (see
Figure 3.7(a));
(b) sumps do require an increase in the depth of flow in the box gutter and are either —
(i) side overflow (see Figure 3.7(b)); or
(ii) high-capacity overflow (see Figure 3, 7(c)) where in the event of a blockage in
the normal vertical downpipe A the water level in the primary sump B will rise
to and overtop the overflow weirs CI and C2 (each weir length equal to the
width of the adjacent box gutter) to flow either directly, or indirectly by the
overflow channel D, to the secondary sump E and then to the overflow vertical
downpipe F,
1 A vertical pipe overflow, where for example downpipe F (Figure 3.7(c)) projects
through the floor of the sump, is a possible alternative where a high-capacity
device is not required. No equations, graphs or examples are provided for vertical
pipe overflow devices due to a lack of appropriate research data. It is recommended
that vertical pipe overflows be designed by suitably qualified competent persons
taking into account the water profile in the gutter upstream of the overflow device.
2 Where water flowing directly into the overflow is a problem, a deflector or cap
may be installed to divert the water.
3.7.6 Downpipes
Downpipes shall —
(a) be fitted vertically to the base of a rainhead or sump; and
(b) discharge to —
(i) a rainhead or sump of a lower gutter (see Clause 3.4.5); or
(ii) the surface water drainage system.
3.8 SOAKERS
NOTE: Data for the design of soakers is the subject of research and when available will be
considered for adoption in the Standard.
COPYRIGHT
AS/NZS 3500.3:2003
36
Rainhea
Overflow weir
Downpipe
Box gutter
Wall
(a) Rainhead
V— Overflow duct or channel
X gutter
npipe
(c) Sump/high capacity overflow device (see Clause 3,7,2,2(b)(ii))
NOTES:
1 Layout of sump/side overllow device may have to be varied due to constraints (see Figure 3.7(b)).
2 Where desired, the sides of the sump/high-eapaeity overllow device may be perforated to flush the
downpipe (F) (see Figure 3.7(c)).
3 The normal outlet may be moved longitudinally to enable better inspection and maintenance access (see
Clause 3.7.4 (f)) (see Figure 3.7 (c)).
4 For criteria for overflow devices see Clause 3.7.5.
FIGURE 3.7 OVERFLOW DEVICES— BOX GUTTERS
COPYRIGHT
37
A S/N/.S 35003:2003
( START ^
:^
Determine the ARI from Clause 3.3.4 (Table 3.1),
For convenience this flow chart assumes that ARI of
100 years for Australia and 50 years for New Zealand are selected.
If other ARI are selected, adjust the flow chart to suit.
(b)
Determine the rainfall intensity for the site from Clause 3.3.5.
For Australia, see Appendix E Figures - Rainfall intensities (mm/hr) for 5 min
duration and an ARI of 100 years. (Referred to as ^^^I^).
For New Zealand, see Appendix F Figures and determine ^O/iQ'
See Appendix D for Guidelines for rainfall intensities.
L
t^\ I Obtain dimensions and other relevant data from physical observations and
measurements, plans or both, (See Paragraph J2, Appendix J for an example.
(d)
(e)
7
Select position of box gutter, expansion joint(s) and outlet(s) based on approximate maximum
catchment from Figure 11 for 16 L/s flow and site rainfall intensities,
Determine catchment area A^ for each section of box gutter and each outlet. (See Clause 3.4)
Determine the design flows (O) from Figure II using O^^I^] or {^^I^q) and /l^ . Design each bo>
gutter and rainhead separately.
(9)
Ih)
f STOP V
Beyond scope
of general method
Yes
Subsequent trials
A^ needs to be reduced.
Review selections at (d). An
increase in the number of
outlets may require sumps
rather than rainheads.
Determine sole width iw^^] and gradients of box gutter, from Figure II using the design flow.
(i) Determine the actual minimum depth of the box gutter [h^] from Figure II using O, w^^q, and gradient.
(J)
(k)
\\/
Select a size of vertical downpipe and total depth of rainhead ( h,-) from Figure 13.
f
Check if the total depth {h), needs to be adjusted as required by Note 1
of Figure I2 rainhead.
7
Determine the length of rainhead (/,-] from Figure 13.
Determine the size of the rainhead from Figure 12 using/j^, and /^ .
( FINISH }
MOTES:
1 Selected positions of box gutter, expansion joint(s), rainheads, downpipes and overHovv devices shall be
compatible with the layout of buildings and site stormwater drains and the criteria for thermal variation
(see Clause 4.3).
2 Figure 13 is for a box gutter with a gradient of 1:200. For steeper gradients, determine From Figure II, (\:>r
the design How, the equivalent total depth of box gutter with a gradient of 1:200. Determine froiTi
Figure 13, lx)r the equivalent total depth, the increased /,..
FIGURE 3.8 FLOW CHART— GENERAL METHOD FOR DESIGN OF BOX GUTTERS,
RAINHEADS AND DOWNPIPES
COPYRIGHT
AS/NZS 3500.3:2003
38
C
START
3
Determine the ARI from Clause 3.3.4 [Table 3,1).
For convenience this flow chart assumes that ARI of
100 years for Australia and 50 years for New Zealand are selected.
If other ARI are selected, adjust the flow chart to suit.
J£
Determine the rainfall intensity for the site from Clause 3.3.5.
For Australia, see Appendix E figures - Rainfall intensities (mm/hr) for 5 min
duration and an ARI of 100 years, (Referred to as 100/5 )
For New Zealand, see Appendix F figures and determine 50/.
See Appendix D for guidelines for rainfall intensities.
10'
Obtain dimensions and other relevant data from physical observations and
measurements, plans or both. See Paragraph J3, Appendix J for an example.
Select position of box gutter, expansion jointis] and outlet(s) based on approximate
maximum catchment from Figure II for 16 L/s and site rainfall intensities.
:ik_
Determine catchment area [A^] for each section of box gutter and each outlet,
(See Clause 3.4)
-^
(f)
(g)
Determine the design flows [Q] from Figure II using [IOO/J or (50/^q) and A^. Design each
sump/side overflow device and associated box gutters separately.
^_
Determine sole width (^Vbg) and minimum depth of box gutter (/Vg) for free flow conditions
from Figure II for the box gutter with the maximum flow.
(h)
C
Stop
Beyond scope of
general method
C
Stop
Beyond scope of
general method
Aq needs to be reduced.
Review selections at (d).
Possible measures include
repositioning outlets and
expansion joints, increasing
the number of outlets, or a
combination of measures,
FIGURE 3.9 (in part) FLOW CHART— GENERAL METHOD FOR DESIGN OF BOX
GUTTERS, SUMP/SIDE OVERFLOW DEVICES AND DOWNPIPES
COPYRIGHT
39
A S/^ZS 35003:2003
(j)
(k)
(I)
Select downpipe from Figure 14 for the total design flow through the outlet,
Determine the depth of sump (A?s).
Determine the minimum horizontal distance between the sides of the overflow channel and
those of the sump ( /qc ) ffom Figure 16(a) for the largest flow in any one box gutter.
Select the width of the overflow channel (m/qc) and determine minimum depth of
overflow channel Oqc •
Determine the minimum height of the top of the box gutters above the crest of the
overflow channel weir A?t = (/oc + (<^oc+ 30)) - (0.7 /qc ) = 170 mm
Review selection of
overflow channel width
i^oc at (I), or selection
of box gutter width
Determine the size of sump/side overflow device and sump from Figure 16
C FINISH J
NOTES:
1 Selected positions of box gutter, expansion Joint(s), sumps, downpipes and overllow devices to be
compatible with the layout of buildings and site stormwater drains and the criteria for thermal variation
(see Clause 4.3).
2 The total design flow is the summation of the design flow for each box gutter and the section of roofing
discharged directly into the sump.
FIGURE 3.9 (in part) FLOW CHART— GENERAL METHOD FOR DESIGN OF BOX
GUTTERS, SUMP/SIDE OVERFLOW DEVICES AND DOWNPIPES
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AS/NZS 3500.3:2003
40
c
START
^
Determine the ARI from Clause 3.3.4 [Table 3.1).
For convenience this flow chart assumes that ARI of
100 years for Australia and 50 years for New Zealand are selected.
If other ARI are selected, adjust the flow chart to suit.
-£-
(b)
Determine the rainfall intensity for the site from Clause 3.3.5,
For Australia, see Appendix E figures - Rainfall intensities (mm/hr) for 5 min
duration and an ARI of 100 years, (Referred to as 100/^ ).
For New Zealand, see Appendix F figures and determine 50/.^. ,
See appendix D for guidelines for rainfall intensities.
:i_
Obtain dimensions and other relevant data from physical observations and
measurements, plans or both. (See Paragrapfi J4, Appendix J for an
example.)
(d)
(e)
(f)
(g)
Select position of box gutter, expansion joint(s) and outlet(s) based on approximate
maximum catchment from Figure II for 16 L/s flow and site rainfall intensities.
T
Determine catchment area /l^ for each section of box gutter and each outlet,
(See Clause 3.4).
Determine the design flows (O) from Figure II using ( lOO/c) or (50/.^) and /l^
Design each sump/high capacity overflow device and associatea box gutters separ
eparately.
Determine sole width iw^^ and maximum depth of box gutter (h^] for free flow
conditions from Figure II for the box gutter with the maximum flow.
(h)
r Stop ^V-
Yes
Subsequent trials
Beyond scope of
general nnethod
f Stop \
Beyond scope of
general nnetfiod
Yes
Yes
First trial
A^ needs to be reduced,
Review selections at (d).
Possible measures include
repositioning outlets and
expansion joints, increasing
the number of outlets, or a
combination of measures.
FIGURE 3.10 (in part) FLOW CHART— GENERAL METHOD FOR DESIGN OF BOX
GUTTERS, SUMP/HIGH-CAPAGITY OVERFLOW DEVICES AND DOWNPIPES
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41
AS/N/S35(»0.3:2003
(j)
(k)
Select downpipe from Figure 14 for the total design flow through the outlet.
Determine the depth of sump ihs) which shall not be less than 150 mm (See Clause 3.7,4)
Determine the height of the overflow weirs (/qcI above the sole of the box gutter from
Figure 16(a) for the largest flow in any one box gutter.
Determine the minumum height of the box gutter above the top of the overflow weirs (^t)
from Figure 16(a) for the largest flow in any one box gutter.
Yes
-iK-
Minimum depth of box
gutter c^bg = (^t + ^oc )
No
Minimum depth of box
gutter c/bg^^a
Yes
(Pl
The datum level for the
depth of the sump is the
sole of the box gutter
No
_^
The datum for the
depth of the sump
is the downstream
sole of the overflow
channel (60 - /qc )
below the sole of the
box gutter
Determine the size of sump/high overflow device and sump from Figure 17,
using the required datum level, ^g ^^^ ^oc
The depth of the sump shall not be less than 150 mm
c
N/
FINISH
3
NOTBS:
1 Selected positions of box gutter, expansion Joint(s), sumps, downpipes and overflow deviees shall be
compatible with the layout of buildings and site stormwater drains and the criteria for thermal variation
(see Clause 4.3).
2 The total design How is the summation of the design t1ow for each box gutter and the section of roofing
discharged directly into the sump.
FIGURE 3.10 (in part) FLOW CHART— GENERAL METHOD FOR DESIGN OF BOX
GUTTERS, SUMP/HIGH-CAPACITY OVERFLOW DEVICES AND DOWNPIPES
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AS/N/^S 3500.3:2003 42
SECTION 4 ROOF DRAINAGE SYSTEMS—
INSTALLATIONS
4.1 SCOPE OF SECTION
This Section specifies installation requirements for roof drainage systems.
4.2 TRANSPORT, HANDLING AND STORAGE
4.2.1 General
Roof drainage system components and support systems shall be transported, handled and
stored with care so that no damage occurs during these operations. When stored on site they
shall be in sheltered and secure positions.
4.2.2 Strippable polymer coating
Strippable polymer coatings shall be removed from components during installation.
4.3 THERMAL VARIATION
4.3.1 General
Where thermal variation of roof drainage system components or support systems, or both,
would otherwise have a deleterious effect, adequate provision shall be made to
accommodate such variation. Where thermal variation is to be controlled, the restraint shall
be limited to one fixed point per section and due allowance shall be made for the forces that
will be imposed by it.
4.3.2 Expansion joints
Expansion joints shall comply with the following:
(a) Box gutters For box gutters and support systems, the maximum lengths between
expansion joints and minimum expansion space shall be as given in Table 4.1. The
gaps between the stop ends shall be bridged by a suitable saddle flashing. The
maximum lengths between expansion joints in Table 4.1 shall apply from the fixed
point to the free end/s.
(b) Eaves gutters Eaves gutters shall have support systems that permit longitudinal
thermal expansion without detriment to the gutter or accessories.
(c) Downpipes Downpipes shall have support systems that permit thermal expansion
without detriment to the downpipe or accessories.
NOTE: The temperature variation experienced by products will depend upon geographical
location, extent of shading and absorptivity and surface colour. During summer, in most parts
of Australia and New Zealand, the temperature of products exposed to direct sunlight may
exceed 80°C.
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AS/N/.S 3500.3:2003
4.4 CORROSION
4.4.1 Corrosion due to direct contact
Metal roof drainage system components, including accessories and fasteners, and, where
applicable, metal cladding shall be designed with either —
(a) compatible metals in direct contact (see Table 4.2); or
(b) where unavoidable, incompatible metals separated by an impervious non-conducting
material.
NOTES:
1 Combinations of metals, given in Table 4.2, are based on current knowledge and the premise
that the area of rainwater goods or metal cladding is relatively large in comparison to that of
accessories or fasteners.
2 The resistance of roof drainage system components of certain metals to corrosive agents is
partly dependent on the beneficial washing action of rain and no permanent ponding.
3 The service life of most metals in severe marine atmospheres and industrial areas with
atmospheres contaminated by acid-bearing agents can be extended by the use of special
painting procedures (see AS/NZS 2312).
4.4.2 Corrosion due to drainage
Metal roof drainage system components shall be designed and installed to prevent
corrosion, erosion, or both, due to drainage from metal and non-metal roof drainage system
components and, where applicable, cladding.
ISIOTE: Table 4.3 gives guidance on combinations for materials to prevent corrosion, erosion, or
both, due to drainage.
TABLE 4.1
BOX GUTTERS AND SUPPORT SYSTEMS—MAXIMUM LENGTH BETWEEN
EXPANSION JOINTS AND MINIMUM: EXPANSION SPACE
Material
Coefficient
Base
metal
Maximum length between
expansion joints
Minimum
expansion space
of thermal
thickness
m
mm
expansion
per °C
One end fixed
Both ends free
mm
and
one end free to
move
to move
Aluminium
24 X 10"^^^
0.90
12
24
50
1.00
12
24
Copper
17x1 Q-^
0.60
9
18
50
0.80
15
30
1.00
26
52
Steel
12 X \(y^'
0.55
20
40
50
0.75
25
50
Stainless steel
\7 xur''
0.55
20
40
50
PVC
70 X 10^^
—
10
20
30
Zine
26 X 10^^
0.80
10
20
50
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AS/NZS 3500.3:2003 44
4.4.3 Corrosion due to crevices
Metal roof drainage systems and support systems shall be designed and installed to achieve
complete drainage or drying. Shielded areas capable of causing permanent ponding shall be
avoided to prevent the possibility of intense localized corrosion known as crevice corrosion.
>JOTE: Tills type of attack results from contact of metal with moisture and salts under oxygen-
deficient conditions where trapped moisture cannot readily evaporate. It can be caused by lap
joints, absorbent gaskets, holes, crevices under bolt or rivet heads or surface deposits including
non-metallic materials, such as elastomeric materials, plastic, fabrics, lifted paint films or
accumulated solids.
4.4.4 Corrosion dues to chemical incompatibility
Bedding materials used in conjunction with roof drainage systems shall be chemically
compatible. Cement-based bedding may be used between tiles and valley gutters other than
those of exposed aluminium/zinc alloy coated steel,
4.5 INSTALLATION AND TESTING
4.5.1 Installation
Installation of each new, or altered section of the roof drainage system shall be in
compliance with the following:
(a) There shall be no restrictions to the free flow of stormwater due to —
(i) protrusions or other obstructions; or
(ii) debris, e.g., cement, mortar, clippings, and similar.
(b) All accessories shall be effectively fixed and securely anchored.
4.5.2 Testing
Downpipes within buildings shall comply with Section 10.
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o
o
<
o
TABLE 4.2
COMPATIBILITY OF DIRECT CONTACT BETWEEN METALS
Accessory or
fastener material
Fastener material
Roof drainage system
components and any
Aluminium
alloys
Copper and
copper alloys'^
Stainless steel
(300 series)
Zinc-coated steel
and zinc
Aluminium/zinc
alloy-coated steel
Lead
Ceramic or organic
coated
cladding material
Atmospheric classif
ication
SI and VS
Mild
Sland VS
Mild
SlandVS
Mild
SI and VS
Mild
SlandVS
Mild
SlandVS
Mild
SI, VS and Mild
Aluminium alloys
Yes
Yes
No
No
t
Yes
+
Yes
Yes
No
No
Yes
Copper and copper alloys
No
No
Yes
Yes
No
Yes
No
No
No
No
No
Yes
Yes
Stainless steel (300 series)
No
No
No
No
Yes
Yes
No
No
No
No
No
Yes
Yes
Zinc-coated steel and zinc
Yes
Yes
No
No
No
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Aluminium/zinc alloy-
coated steel
Yes
Yes
No
No
No
Yes
+
Yes
Yes
No
No
Yes
Lead §
No
No
Yes
Yes
Yes
Yes
No
Yes
No
No
Yes
Yes
Yes
"^ Includes monel metal rivets.
t Grade 316 in accordance with ASTM A240 is suitable.
J Unpainted zinc-coated steel and zinc are suitable for direct contact but should not receive drainage from an inert catchment.
§ Due to its toxicity, lead is not recommended for rainwater goods.
LEGEND:
SL VS, Mild = severe industrial, very severe and mild classifications (see AS/NZS 2312).
Yes = acceptable — as a result of bimetallic contact, either no additional corrosion of rainwater goods will take place, or at the worst, only very slight
additional corrosion. It also implies that the degree of corrosion would not significantly shorten the service life.
No = not acceptable — moderate to severe corrosion of rainw'ater goods will occur, a condition which may result in a significant reduction in the service
life.
NOTE: Unless adequate separation can be assured, prepainted rainwater goods should be considered in terms of the base metal or coated metal product.
N
o
o
<
G)
TABLE 4.3
COMPATIBILITY OF DRAINAGE FROM AN UPPER SURFACE
TO A LOWER METAL SURFACE
Upper cladding or roof drainage system material
Lower roof
drainage system
material
Aluminium alloys
Copper and
copper alloys
Stainless
steel
(300 series)
Zinc-
coated
steel and
zinc
Aluminium/
zinc alloy-
coated steel
Lead
Prepainted
metal
Roof tiles
Plastic
Glazed
Unglazed
Glass
Aluminium alloys
Yes
No
t
Yes
Yes
*
Yes
Yes
Yes
Yes
Yes
Copper and copper
alloys
^
Yes
*
*
*
Yes
^
Yes
Yes
Yes
Yes
Stainless steel (300
series)
*
^
Yes
*
*
Yes
*
Yes
Yes
Yes
Yes
Zinc-coated steel
and zinc
No
No
No
Yes
No
*
No
No
Yes
No
No
Aluminium/zinc
alloy- coated steel
Yes
No
*
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes
Lead
^
*
*
^
*
Yes
*
Yes
Yes
Yes
Yes
* Whilst drainage between the materials shown would be acceptable, direct material contact should be avoided (see Table 4.2).
LEGEND:
Yes = acceptable No = not acceptable
NOTE: 'Acceptable' and 'not acceptable' imply similar performances to those noted in Table 4.2.
S
4^
47 AS/N/S 3500.3:2003
4.6 INSPECTION AND CLEANING
NOTES:
1 Sizing of stormwater drainage installations assumes that the responsible owner or manager
arranges regular inspection and cleaning to remove any obstructions that would reduce the
installation's hydraulic capacity or design lifetime, or both.
2 Obstructions that could cause partial or complete reduction in the hydraulic capacity are
windborne plastics, drink cans, builders' refuse, balls, bird nests, items deposited by birds,
dead birds, leaves, moss, mortar, silt or similar.
3 Guards on gutters and gutter outlets and screens on outlets from on-site stormwater detention
(OSD) facilities are installed to prevent reduction in hydraulic capacity due to obstructions.
Installation of such guards and screens does not eliminate the need for regular inspection and
cleaning. Guards used with rainwater goods might collect debris during high intensity storms,
in spite of regular inspection and cleaning, and for this reason it might be better not to install
such guards, particularly on box gutter sumps,
4.7 ALTERATIONS AND DISCONNECTION
NOTES:
1 Disused roof drainage system components, including overflow devices, should be removed
and any resulting openings to the remaining roof drainage system or surface-drainage system
should be sealed in a manner appropriate for the material remaining in use.
2 Disused accessories and fasteners should be removed and any damage to the building made
good in a manner appropriate for the material damaged.
4.8 EAVES GUTTERS
Eaves gutters shall be installed as follows:
(a) Gradients Deviations from nominal gradients shall be smooth and not cause
permanent ponding.
NOTES
1 Where a building is likely to move due to reactive soils, gradients may need to be not
flatter than—
(a) 1 :250 to achieve an effective gradient not flatter than 1 :500; or
(b) 1 :500 to achieve an effective gradient with no permanent ponding.
2 Light condensation will not generally cause permanent ponding whereas heavy
condensation, particularly in conjunction with retained silt, can reduce the design lifetime
of the product.
(b) Lap joints For metal gutters with laps between 20 mm to 25 mm the lap shall be
fully sealed. Wider laps shall be sealed and fastened at each end of the lap rather than
filling the total area.
(c) Support systems Support systems shall comply with Clause 4. 16.
4.9 BOX GUTTERS
Box gutters shall be installed as follow^s:
(a) Gradients Gradients shall be not flatter than 1:200 for sole widths equal to or less
than 600 mm wide. Deviations from these gradients shall be smooth and not cause
permanent ponding.
(b) Lap joints Lap joints shall be in accordance with Clause 4.8(b).
(c) Support systems Support systems shall be in accordance with Clause 4.8(c).
(d) Outlets Outlets shall discharge through either a rainhead or a sump.
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AS/NZS 3500.3:2003 48
(e) Expansion joints Where necessary, expansion joints shall be provided (see
Clause 4.3). All fixings shall be in the form of cleats and clips to allow freedom of
movement.
>JOTE: The sides of a box gutter should have adequate structural strength so that water pressure
will not cause deformation that can affect water surface levels and hence the hydraulic capacity of
a box gutter.
4.10 VALLEY GUTTERS
Valley gutters shall be installed as follows:
(a) Lap joints Lap joints shall be in accordance with Clause 4.8(b) and 150 mm min. lap
for an unsealed joint.
(b) Support systems Support systems shall be in accordance with Clause 4.8(c).
(c) Edges Edges shall be rolled or returned to prevent splashing.
4.11 DOWNPIPES
Downpipes shall be installed as follows:
(a) Locations Downpipes shall be located —
(i) so that they do not interfere with the normal operation of any door, window,
access opening or occupancy of a building;
(ii) where they do not cause a nuisance or lead to injury of a person;
(iii) as close as practicable to the supporting structure;
(iv) so that they are adequately protected from mechanical damage;
(v) at least 1 00 mm clear of any electrical cable or gas pipe; and
(vi) at least 50 mm from any other pipework or service.
(b) Concealment or limited access Downpipes in buildings may be concealed or have
limited access provided —
(i) the inspection openings (see Item (d)) are accessible;
>JOTE: To facilitate maintenance, inspection openings should be extended to the face
of a wall or slab,
(ii) the installation complies with the manufacturer's recommended installation and
maintenance procedures for the materials and products;
(iii) the seams and joints are watertight; and
(iv) unless otherwise directed by an engineer, they are —
(A) clear of any structural member, e.g., beam, or column, or party wall; or
(B) not concealed in any dry wall construction that could interfere with the
structural integrity of the wall.
(c) Connections within buildings Where a downpipe is connected to a site stormwater
drain located below a slab-on-ground, the connection shall be located above the level
of the tloor.
(d) Inspection openings Inspection openings for testing and maintenance purposes shall
have a nominal size of not less than nominal diameter of the downpipe.
(e) Support systems The support systems shall comply with Clause 4.16.
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49 AS/N/S 3500.3:2003
4.12 OVERFLOW DEVICES OR MEASURES
Overflow devices for box gutters shall comply with Clause 3.7.5. Overflow measures for
eaves gutters shall comply with Clause 3.5.3.
4.13 JOINTS FOR METAL COMPONENTS
4.13.1 General
Compatibility of materials shall be in accordance with the requirements of Table 4.2 and
Table 4.3.
4.13.2 Type of joints
4.13.2.1 Soldered
Soldered joints shall be clean and free from grease, and shall be flush and lapped in the
direction of the outlets, as specified, and completely sweated with solder to form a secure
joint that does not cause permanent ponding. Immediately after cleaning, the surfaces to be
jointed shall be painted with the appropriate flux given in Table 4.5.
NOTES:
1 60/40 or 80/20 tin/lead solder can enhance the surface finish of stainless steel.
2 Because of the risk to health and safety, care should be exercised during the preparation and
handling effluxes.
The laps for —
(a) eaves gutters, shall be —
(i) for in-line joints, not less than 25 mm; and
(ii) for all other joints, as specified by the manufacturer; and
(b) box gutters fasteners shall be spaced at not more than 40 mm centres and not less than
10 mm from the edges of the joint.
4.13.2.2 Sealant
Sealant joints shall be used in conjunction with mechanical connections or fasteners as
specified in AS/NZS 2179.1, spaced at not more than 40 mm centres. The sealant shall be
sandwiched between clean surfaces of the components of the joint to ensure a positive seal
and to protect the sealant from exposure to ultraviolet radiation. To ensure complete cure of
silicone rubber sealants, the width of sealant bead, when compressed, should not exceed
25 mm.
Laps shall be as for soldered joints, as appropriate.
TABLE 4.5
FLUXES
Material to be joined
Type of flux
Zinc-coated steel
Dilute hydrochloric acid*
Copper and copper alloy
Zinc chloride (killed spirits)
Stainless steel
Phosphoric acid based Hux tor soldering!
Zinc
Zinc chloride (killed spirits)
* Muriatic acid. 1:3 dilution of hydrochloric acid.
t Chloride-based Huxes are not used.
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AS/N/S 3500.3:2003 50
4.13.3 Aluminiuin alloys
Aluminium alloy components including accessories shall be jointed with one of the
following:
(a) Brazed joints Brazed joints shall have a minimum lap and shall be brazed with
aluminium/silicon alloys containing 11.5 ±1.5% silicon. Lower melting point
aluminium/silicon alloys shall not be used, Flux-aflected areas shall be thoroughly
washed with water to prevent subsequent corrosion.
(b) Welded Joinis Welded joints shall be shop fabricated and be either the gas metal-arc
welding (GM AW) or gas tungsten-arc welding GTA W type (see AS 1 665),
(c) Soldered joints Soldered joints shall not be used with aluminium alloys due, in the
presence of moisture, to galvanic action.
NOTES:
1 Field fabrication should be limited to joints that are fully protected from air movement and
moisture.
2 GMAW and GTAW types are also known as MIG and TIG welding types, respectively.
4.13.4 Aluminium/zinc alloy-coated steel
Aluminium/zinc alloy-coated steel components, including accessories, shall be jointed with
sealant joints and fasteners as specified in Clause 4.13.1.2.
4.13.5 Stainless steel
Stainless steel components including accessories shall be jointed with one of the following:
(a) Sealant joints Sealant joints shall be as specified in Clause 4.13.1.2,
(b) Soldered joints Soldered joints shall be as specified in Clause 4.13.1.1.
(c) Welded joints Welded joints shall be either —
(i) spot welds at normal rivet centres, i.e., about 40 mm, and sealed with either
solder by sweating from the inside or sealant; or
(ii) continuous weld.
Where material thickness allows, GMAW or GTAW may be used.
4.13.6 Zinc and zinc-coated steel
Zinc and zinc-coated steel components, including accessories, shall be jointed with one of
the following;
(a) Sealant joints Sealant joints shall be as specified in Clause 4.13.1.2.
(b) Soldered joints Soldered joints shall be as specified in Clause 4,13.1 .1 .
4.14 JOINTS FOR PVC COMPONENTS
Joints for PVC components, including accessories, shall comply with AS/NZS 2179.2(lnt).
4.15 JOINTS FOR OTHER COMPONENTS
Joints for other components of similar and dissimilar metals and non-metals shall be as
given in Table 4.6.
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51
AS/NZS 3500.3:2003
TABLE 4.6
PERMISSIBLE JOINTS FOR OTHER COMPONENTS OF SIMILAR OR
DISSIMILAR MATERIALS
From mate
rial 1
To material
Cast iron
Copper
2
Aluminium
alloy
and
ductile
iron
and
copper
alloy
Galvanized
steel
FRC*
GRP
PVC
PE
Aluminium
BG MC
BG
BG BG
BG
alloys
ES WDt
BR
ES
—
ES
ER
—
—
BS
SC/ER
■ —
Cast iron
BG
BG
BG
BG
BG
BG
BG
and ductile
BS
ES
SB/ER
ER
ES
ES
BS
iron
ER
ER
ER
SC/ER
Copper and
__
BG
SB
BG
BG
BG
SC/TII/
IVIVI^II
copper alloy
ER/SB
ES
SS
IH/SB
ER/SB
ER
li^S
SB
SC/ER/
SB
BS
Til/Ill
TI-I/SS
Galvanized
BG
BG
SB/ 111
111 BG
ER
BG
SC/TH
—
steel
ES
ER
SB/ER
MC
ER
SC/BR
FRC*
—
BG ER
ES
BG
ER
ER
BG ER
ES
—
ES
ER
—
GRP
BG ER
ES
BG
ER
ES
PVC
BG
BG
SB/TH/SC
TH/SC
BG ER
SC
sc/ni
ES
ES
ER/SC
SB/ER/SC
ES
ER/SC
ES
ES
PC
PE
BG
ES
■
rij/Bh^
TH/TH
SS/TH
~"
—
rii/sc
Bl' Til
EF ES
MC FE
* Under buildings limited to ES.
t Eimited to shop GTAW for thicknesses equal to or greater than 0.7 mm.
LEGEND
Symbol
Joint type
Reference
Symbol
Joint type
Reference
BE
Butt fusion
MC
Mechanical coupling
AS 1761
BG
Bolted gland
2.8.2.1
SB
Silver brazed
2.8.2.8
EE
Blectrofusion
SC
Solvent cement
2.8.2.10
ER
Epoxy resin
2.8.2.4
SS
Soft solder
2.8.2.9
ES
Elastomeric seal
2.8.2.3
TM
Threaded
2.8.2.1 1
EC
Metal-bonded
flexible coupling
2.8.2.6
WD
GMAW or GTAW
AS 1665
PL
Flanged
AS 4087
NOTES:
1 The direction of How is to be from material 1 to material 2.
2 Where joint types are separated by one or more slashes, the joint between pipe materials
requires an appropriate transition fitting or adaptor.
3 Joints of dissimilar materials shall comply with Clause 4.4.
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AS/NZS 3500.3:2003 52
4.16 SUPPORT SYSTEMS
4.16.1 Types
The types of support systems are either non-trafTicable or trafficable (see vertical load test
of AS/NZS 2179.1) and may be discontinuous or continuous.
4.16.2 Criteria
Support systems shall —
(a) be fabricated from materials that —
(i) are compatible with the supported roof drainage system; and
(ii) where exposed to direct sunlight, are resistant to ultraviolet light;
NOTE: Incompatible materials may be used provided the contact surfaces are lined
with a non-abrasive, impervious, non-conducting material.
(b) be securely attached to the building structure;
(c) have no other service attached to them or be attached to any other service;
(d) be protected against corrosion where exposed to a corrosive environment; and
(e) be securely attached to prevent longitudinal movement, unless designed to allow for
thermal effect.
4.16.3 Support systems for eaves gutters
Support systems for eaves gutters manufactured from —
(a) metals shall comply with AS/NZS 2179.1;
(b) PVC shall comply with AS/NZS 2179.2(]nt); and
all eaves gutters and their support systems shall be non-trafficable.
4.16.4 Support systems for box gutters
Support systems for box gutters manufactured from —
(a) metals shall comply with AS/NZS 2179.1; and
(b) PVC shall comply with AS/NZS 2179.2(Int).
Such support systems shall be either —
(i) continuous, where the support extends across the sole width for the full length of the
gutter and provides a direct evenly distributed contact to not less than 25% of the sole
width; or
(ii) discontinuous, where the support brackets extend across the sole width of the gutter
and are located at stop ends, both ends of sumps, rainheads and intervals not greater
than 750 mm, or are located in accordance with manufacturers instructions.
NOTES:
1 Continuous support systems should be used for sole widths greater than 450 mm.
2 For the design loads for support systems (see AS/NZS 1 170.1).
4.16.5 Support systems for valley gutters
Support systems for valley gutters manufactured trom—
(a) metals shall comply with AS/NZS 2179.1; and
(b) PVC shall comply with AS/NZS 2179.2(int).
NOTB: For the design loads for support systems refer to AS/MZS 1 170.
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4.16.6 Support systems for downpipes
4.16.6.1 Vertical
Support systems for vertical downpipes manufactured from —
(a) metals shall comply with AS/NZS 2179.1; and
(b) PVC shall comply with AS/NZS 2179.2(lnt).
4.16.6.2 Graded
Support systems for graded downpipes of —
(a) metals shall comply with AS/NZS 2179.1; and
(b) PVC shall comply with AS/NZS 2179.2(lnt).
Jointed pipes and fittings shall have support spacing —
(i) for aluminium alloys, not exceeding 2000 mm;
(ii) for cast iron, ductile cast iron, copper, copper alloys, galvanized steel and stainless
steel, not exceeding 3000 mm;
(iii) for FRC and GRP, not exceeding 4000 mm;
(iv) for PVC, as specified for pressure pipe systems in AS 2032; and
(v) for PE, as specified for pressure pipes above ground in AS 2033.
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SEC T I O N 5 S U R FACE D R A 1 N A G E
S Y S T E M S ^ D E S I G N
5.1 SCOPE OF SECTION
This Section specifies methods for the design and procedures for surface drainage systems.
5.2 DESIGN METHODS
5.2.1 Methods
This Section provides two design methods, as follows:
(a) The general method (see Clause 5.4)
(b) The nominal method (see Clause 5.5).
Either method may be used within the specified limitations.
5.2.2 General criteria
Piped systems shall meet the minimum pipe diameter, cover and gradient criteria specified
in this Standard. Such systems shall be arranged so that any overflows will not pond
against, or enter into buildings.
5.2.3 Design rainfall intensity
Elements shall be designed to contain within surface drains, gutters or formed flow paths
minor storm events of the appropriate average recurrence interval (ARl) specified in
Table 5.1. Surface drainage systems shall be designed to ensure overflows, in storm events
with an ARl of 100 years in Australia or 50 years in New Zealand, do not present a hazard
to people or cause significant damage to property.
5.3 LAYOUT
5.3.1 General
Layouts of surface drainage systems should take full advantage of the existing and proposed
topography of the site and the position and level of the point or points of connection to the
stormwater drainage network.
5.3.2 Influences on layout
Factors that determine a layout include the following:
(a) Site conditions, including —
(i) the intended uses of existing and proposed buildings;
(ii) location of downpipes and overflow devices, where appropriate, surcharge
outlets and outlets of any internal drainage or pump-out systems;
(iii) any stormwater discharges from adjacent land;
(iv) location of existing and proposed pervious and impervious areas, such as paved
areas, parking lots and gardens;
(v) soil types and strata, and vegetative cover and trees;
(vi) locations of access to the site, and to ground-level and below-ground floors of
buildings (see Clause 5.3.3.4);
(vii) location of existing and proposed services, e.g., sanitary drains, water services
and similar;
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(viii) works necessary to protect buildings and other services during the installation
of the surface water drainage system;
(ix) works necessary to protect the surface water drainage system during the
construction of proposed buildings and other services;
(x) location of special drainage facilities, such as on-site stormwater detention
storage areas and tanks; and
(xi) location of existing and proposed arresters to reduce contaminants, e.g.,
petroleum products, leachate from rubbish tips on industrial or commercial
sites.
(b) Provision for overland flow paths for the safe disposal of stormwater flows due to
discharge from —
(i) roof drainage system overflow devices due to blockages of downpipes;
(ii) surcharged site stormwater drains or point(s) of connection, i.e., surcharge
outlets or inlet pits; or
(iii) rainfall events with an ARI greater than the design ARI, allowing for possible
discharges from adjacent areas.
5.3.3 General criteria for layouts
5.3.3.1 Roof areas
Stormwater from roof areas shall, in general, be collected and conveyed in gutters and
downpipes (see Section 3) and, during periods of high rainfall intensity or blockage of the
roof drainage system, be discharged through overflow devices —
(a) to site stormwater drains or channels;
(b) to paved areas; or
(c) to—
(i) impinge onto concrete or stone splash blocks and then infiltrate into pervious
areas; or
(ii) discharge to subsoil drains or soakaways, either directly, i.e., by pipe, or
indirectly, i.e., by infiltration.
NOTE: Such systems may be desirable in areas with permeable soils, as a means of
reducing the discharge of stormwater or increasing the water table; however, in areas
with impervious soils, such systems may cause waterlogging of land and dampness in
buildings. Where soils are expansive, damage may occur to footings. Consequently, all
proposals for these systems may be required to be authorized by the regulatory
authority.
5.3.3.2 Other than roof areas
Stormwater from other than roof areas shall, in general, be collected and conveyed via site
stormwater channels and inlets to site stormwater drains.
5.3.3.3 Ponding
Except for on-site stormwater detention (OSD) systems (see Clause 5.4. 1 3), ponding of
stormwater shall only occur temporarily at sag pits complying with Clause 5.4. 10.1.
NOTES:
1 Where the ground floor of a building is lower than the adjacent land, except at access ramps,
the latter should be graded so that there is a reverse slope away from the building to permit
the discharge of stormwater to a site stormwater drain or channel,
2 The ground beneath timber floors and landscaping around and under buildings should be
graded to prevent ponding and permit drainage to the outside of buildings.
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5.3.3.4 Entry into buildings
Storm water shall be prevented from entering doorways and other openings in buildings.
Where these are lower than adjacent ground surfaces, grated drains shall be designed and
placed across ramps or entrances to intercept any flow, which would otherwise drain into
the building.
5.3.3.5 Coniainmenl of harmful substances
Separate surface drainage systems or special arresters (see Clause 8.6) shall be provided for
any parts of the property where materials that could pollute or block such drainage systems
are stored or used. These drainage systems shall comply with the criteria of the network
utility operator regarding containment of polluting substances.
5.3.3.6 Inlet and pit locations
Inlet pits should be located to intercept surface flows, while also fitting neatly into the
layout of the site storm water drains.
On-grade pits situated on sloping surfaces or in channels or gutters shall be sized to
intercept a large proportion of the flow. They shall be located so that any bypass flows
under minor storm event conditions will not cause a nuisance and that widths of
concentrated flow are negotiable by pedestrians.
inlet pits in locations subject to dengue fever borne by mosquitoes shall be without a sump
and be self-draining.
>JOTES:
1 Care should be taken in locating and specifying details of grated pits in areas subject to
pedestrian or vehicular traffic to avoid possible damage to pits and danger to pedestrians and
cyclists.
2 Site stormwater drains should be laid in straight lines —
(a) to avoid conflict with other services; and
(b) to minimize overall length and number of changes in direction.
5.3.3.7 Sanitary drainage system
Surface drainage systems shall be completely separate to any sanitary drainage system.
5.4 GENERAL METHOD
5.4.1 Basis
The general method may be used for all buildings.
Surface drainage systems shall be designed to provide protection against potential losses
caused by any overflows, including damage to buildings and their contents, and injury and
nuisance to persons.
>JOTES:
1 The general method for design of surface drainage systems uses the Rational Formula (see
Equation 5.4.8) to calculate design flows from rainfalls of a given ARI and hydraulic charts to
determine characteristics of the pipes needed to convey such flows. As consequences of
failure may vary at different locations on a property, the ARI can be increased to reflect this.
2 The larger the ARI selected for design, the greater the design rainfall intensity and flow, the
larger the system and, subject to regular inspection and cleaning (see Clause 4.6), the lower
the probability of overflow.
3 Examples that illustrate the application of the general methods are given in Appendix K.
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5.4.2 Overland flood path
Where consequences of failure of a surface drainage system are significant, allowance shall
be made for flows on to the site from adjacent properties. The system shall convey flows
without serious consequences such as entry of water into openings in buildings. If this does
occur, remedial action shall be taken, such as one or more of the following:
(a) Enlargement or extension of the surface drainage system.
(b) Alteration of surfaces and flow paths by regrading and redirection, or provision of
landscaping, bunds and other barriers.
(c) Raising the level of the lowest floor.
5.4.3 ARl
Appropriate values of ARl for design vary according to the importance of the property,
consequences of failure and local practice.
The ARl shall be as given in Table 5.1.
TABLE 5.1
AVERAGE RECURRENCE INTERVALS
Effect of surcharge — Overland flow
ARP,
years
Austra
ia
New Zealand
Small impact, in low density areas
>1
>1
Normal impacts
>2
>2
Ponding in Hat topography; or flooding of parking lots to depths
greater than 150 mm
>10
>]()
Impeded access to commercial and industrial buildings
>10
>10
Ponding against adjoining buildings; or impeded access to
institutional or important buildings (e.g., hospitals, town halls,
school entrances)
>20
>!()
* A higher ARl is appropriate where there is only limited access for maintenance.
TMOTE: For Australia Table 5.1 should be used in conjunction with the BCA which has
requirements to prevent rain and stormwater from entering certain buildings.
5.4.4 Time of concentration
The time of concentration used in the general method for design of surface drainage
systems shall be as follows:
(a) Australia 5 min.
(b) New Zealand 10 min.
5.4.5 Rainfall intensity
The rainfall intensity used in Equation 5.4.8 is determined for a duration equal to the time
of concentration and the selected ARl using design information available —
(a) in Australia from —
(i) the network utility operator, design aids showing rainfall intensities for various
durations and ARls;
(ii) Appendix E, which shows rainfall intensities for 5 min duration and ARls of 20
and 1 00 years; or
(iii) ARR87;and
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(b) in New Zealand from —
(i) the network utility operator, design aids showing rainfall intensities for various
durations and ARls; or
(ii) Appendix F, whieh shows rainfall intensities for 10 min duration and ARls of
10 and 50 years.
MOTE: Design aids are usually in the form of rainfall intensity/frequency duration plots and
tables supplied —
(a) in Australia by the Hydrometeorological Advisory Services of the Bureau of Meteorology
(see Appendix D); or
(b) in New Zealand by the National Institute for Water and Atmosphere (see Appendix D).
5.4.6 Run-off coefficients
The run-off coefficients used in Equation 5.4,8 shall be as follows:
(a) In Australia, they shall have the following values:
(i) For a roofed area, CV equal to 1 .0.
(ii) For an unroofed impervious (paved) area, Cj equal to 0.9.
(iii) For an unroofed pervious area —
(A) as calculated from the following equation:
Cp -m(0.0133"/,o -0.233) • - • 5.4.6
where
Cp = run-off coefficient, for an unroofed pervious area
m = factor dependent on the selected ARl (see Table 5.2)
^^\loo _ Rainfall intensity for a 60-min (1 h) duration and ARl of
10 years, in millimetres per hour but if^ —
(a) less than 25, adopt 25; or
(b) greater than 70, adopt 70
for—
(1 ) clay soils, increase Cp by 0.1; and
(2) sandy soils, decrease Cp by 0.1, provided that the final value of Cp
is not less than 0.1 ; or
(B) as nominated by the network utility operator.
(b) In New Zealand, they shall have the following values:
(i) For a roofed area C, for —
(A) steel and non-absorbent surfaces equal to 0.9; and
(B) near flat and slightly absorbent, equal to 0,8.
(ii) For an unroofed impervious (paved) area, Cj for ground slopes of 1:20 to 1:10
with —
(A) asphalt and concrete surfaces, equal to 0.85; and
(B) store, brick and precast paving panels and —
(1 ) sealed joints, equal to 0.8; and
(2) open joints, equal to 0.60.
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(iii) For an unroofed pervious area, Cp for ground slopes of 1:20 to 1:10, as given
Table 5.3.
For ground slopes other than 1:20 to 1:10, the values given in Items (ii) and (iii) shall be
varied in accordance with Table 5.4.
TABLE 5.2
MULTIPLIERS FOR RUN-OFF COEFFICIENTS
ARB
Years
m
1
0.8
2
0.85
5
0.95
10
1.0
20
1.05
50
1.15
iOO
1.2
greater than 1 00
1.25
Source: ARR87 (except Tor ARls longer than IOO years).
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TABLE 5.3
RUN-OFF COEFFICIENTS (C,,)— NEW ZEALAND
Description of surface
Value for C,,
Description of surface
Value for Cp
Natural surface types
Bare impermeable clay with no
interception channels or run-
olTcontroJ
0.70
Developed surface types
Unsealed roads
0.50
Bare uncultivated soil of
medium soakage
0.60
Railway and unsealed yards
and similar surfaces
0.35
Heavy clay soil types:
— pasture and grass cover
— bush and scrub cover
^cultivated
0.40
0.35
0.30
Land use types
Fully roofed or sealed
developments
0.90
Medium soakage soil types:
—pasture and scrub cover
— bush and scrub cover
—cultivated
0.30
0.25
0.20
Industrial, commercial,
shopping areas and town house
developments
0.65
High soakage gravel, sandy
and volcanic soil types:
—pasture and grass cover
— bush and scrub cover
— cultivated
0.20
0.15
0.10
Residential areas in which
impervious area exceeds 35%
of gross area. (This includes
most modern subdivisions)
0.45
Parks, playgrounds and
reserves:
— mainly grassed
^predominantly bush
0.30
0.25
Gardens and lawns.
0.25
5.4.7 Catchment area
The catchment area used in Equation 5.4.8 for the components of surface drainage systems
shall be the plan area of the catchment, including buildings, draining to a particular
component.
For minor storm events the catchment area is limited to the extent of the property. For
major storm events the catchment area may extend beyond the property (see Clause 5.4.2),
TABLE 5.4
ADJUSTMENT FOR GROUND SLOPE— NEW ZEALAND
Ground slope
Adjustment to values of C^ and Cp
Flatter than 1:20
1:20 to 1:10
1:10 to 1:5
-0.05
Nil
+0.05
Steeper tlian 1 :5
+0.10
5.4.8 Determination of design flows
The general method for the determination of design flows shall be as follows:
(a) Select from Table 5.1 the ARl for the particular application.
(b) Determine from Clause 5.4.5 for the particular location the rainfall intensity, in
millimetres per hour, for the selected ARl and —
(i) 5 mins duration in Australia; or
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(ii) in New Zealand, a duration of —
(A) 5 min, for commercial and industrial developments;
(B) 7 to 10 min, for residential developments; or
(C) 10 min, for low density residential developments.
(c) Determine by physical observations and dimensions or from the relevant plans, or
both —
(i) the layout for —
(A) the downpipes (see Clause 3.7.4(c)); and
(B) the site stormwater drains, including the available gradients and
appurtenances (see Section 8);
(ii) the limits of the sub-catchments for the components of the surface water
drainage systems; and
(iii) for each sub-catchment —
(A) the run-off coefficients based on the extent and type of surface (see
Clause 5.4.6); and
(B) the plan areas of roofed, impervious and pervious surfaces, in square
metres.
(d) Determine the design flow for appropriate sub-catchments of the surface water
drainage system from the following equation:
(c; 4 + q 4 + C\ A^) ^/, i:CA V, • • • 5-4.8
Q = — or
3600 3600
where
Q ~ design flow of stormwater, in litres per second
Ci = run-off coefficient for a roofed area
A, = total roofed catchment area, in square metres
Cj = run-off coefficient for an unroofed impervious (paved) area
A, = total unroofed impervious (paved) catchment area, in square metres
Cp = run-off coefficient for an unroofed pervious area
Jp = total unroofed pervious catchment area, in square metres
/, ^ rainfall intensity for a duration oft and an ARi of Y, in millimetres per
hour
ZCA - equivalent impervious area of all upstream areas on the property, in square
metres
NOTE: No allowance is included for flow from subsoil drains.
5.4.9 Design of open channels
The general method for designing an open channel for a site stormwater drain shall be as
follows:
(a) Determine the design flow, in accordance with Clause 5.4.8.
(b) Determine by physical observation and dimensions or from the relevant plans, or
both, the gradient of the open channel.
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A2
(c) Select a surface type and Manning roughness coefficient (see Table 5.5) and
dimensions for the open channel, then calculate its hydraulic capacity from the
following equation (Manning):
(d)
(e)
Q^ = 1000- «^^^^ s^^^
n
5.4.9
where
Q^ - hydraulic capacity of open channel, in litres per second
A = cross-sectional area of flow in open channel, in square metres
R = hydraulic radius, in metres
.S* = gradient of open channel
n = Manning roughness coefficient for an open channel
If the hydraulic capacity (see Step (c)) is less than the design flow (see Step (a)),
assume a new set of dimensions for the open channel and repeat Step (c) until the
hydraulic capacity exceeds the design How.
Check that the depth of flow in the channel is at least 300 mm below the floor level or
damp course of any adjacent building. If the water level is higher than this limit, the
channel shall be enlarged or its bed lowered to meet this requirement.
TABLE 5.5
MANNING ROUGHNESS COEFFICIENT (n)
Surface type
Typical values for n
Polyethylene (PE)
0.009 to 0.010
Polyvinylchloridc (PVC)
0.009 to 0.010
Smooth concrete
0.011 to 0.012
Trowelled concrete
0.012 to 0.015
Asphalt paving
0.013 to 0.015
Brickwork
0.014 to 0.016
Roughly jointed bricks or pitchers
0.016 to 0.020
Sprayed concrete (gunite)
0.016 to 0.020
Barth- lined channels
0.018 to 0.025
Corrugated metal
0.012 to 0.01 5
Rock lining or rip-rap
0.025 to 0.030
Rock cut
0.035 to 0.040
Grassed or vegetated channels
0.025 to 0.075*
* i;)epending on vegetation growth
5.4.10 Design of inlets
5.4.10.1 Sag pits
The general method for designing an inlet for a sag pit shall be as follows:
(a) Determine the design flow in accordance with Clause 5.4.8.
(b) Determine by observations or relevant plans the maximum depth of ponding, noting
where water may pond against, or enter, a building then the maximum level, unless
otherwise authorized by the network utility operator, shall be not less than 300 mm
below the floor or damp course of the building.
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(c) Calculate the capacity of an inlet, if the depth of ponding is —
(i) equal to or less than 0.12 m, from the following equation:
0-ft, I600PJ;,^ ...5.4.10.1
where
Q, = capacity of an inlet for a sag pit, in litres per second
h[ = blockage factor, inlets to stormwater pits
P = wetted perimeter of an open channel, in metres
dp ~ depth of ponding over inlet, in metres
(ii) or greater than 0.12 m, from street drainage manuals (see the Section on pipe
system drainage in ARR87).
NOTE: A common value for hf is 0.5.
5.4.10.2 On-grade pits
inlet capacities of on-grade pits vary considerably with the shape and size of pit. Blockage
factors are variable, but a value of 0.8 (reducing capacities to 80% of values given by
design aids) shall be used for on-grade pits if no other information is available from the
network utility operator.
NOTE: Reference should be made to street drainage design manuals, manufacturer's literature
and the recommendations.
5.4.1 1 Design of pipe drains
5.4.11.1 General
Pipe drains of site stormwater drains shall —
(a) be laid with even gradients and straight runs and with a minimum number of changes
of direction or change of cross-section, consistent with having adequate hydraulic
capacity;
(b) be laid with any change of direction or cross-section occurring at either an
appropriate fitting or at a pit;
(e) be constructed of materials and products, as specified in Clause 2.5;
(d) have pits and arresters, as specified in Clause 8.6;
(e) have surcharge outlets, as specified in Clause 5.4.12; and
(f) have jump-ups, as specified in Clause 8.9.
5.4.11.2 Design procedure
The general method for designing a pipe drain for a site stormwater drain shall be as
follows:
(a) Determine the design flow, in accordance with Clause 5.4.8.
(b) Determine by physical observation and dimensions or from the relevant plans, or
both, a suitable gradient for the pipe drain.
(c) Select the pipe material and the Colebrook-White roughness coefficient from
AS 2200, or see Table 5.6 for normal conditions, and determine from Figure 5.1 the
hydraulic capacity of the pipe drain for the selected DT^J.
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(d) If the hydraulic capacity is less than the design flow, assume a new DN for the pipe
drain and repeat Step (c) until the hydraulic capacity exceeds the design flow. To
reduce the possibility of overflow from stormwater pits due to increased energy
losses, the full-pipe velocity in the outlet pipe is recommended not to exceed 1.5 m/s
and shall not exceed 2.0 m/s.
TABLE 5.6
COLEBROOK-WHITE ROUGHNESS COEFFICIENT (A)
Pipe material
Typical values for k, mm
Copper, copper alloys, stainless steel
0.015
All plastic pipelines having a smooth (non-profiled)
internal bore
0.015
Fibre-reinrorced conerete (FRC)
0.15
Cast iron, ductile iron, galvanized steel and
malleable east iron
0.6
Vitrified clay, precast conerete
0.6
Corrugated aluminium and steel
3.0
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AS/NZS 3500.3:2003
1000
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66
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^5
....
1
-
100-
-
^
■^
■^
$5
/
^
/
/
^
y^DN
3
^*^<..^^^
/*
^
^^*<..^^^
/
""" ^
'' ^""^
->.'
^
^^'•^^^
^
^
7 - "■-
/ *"
^^
'*
■><
^
'^"S'C^
■^
^
/
-^
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'
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--.DN 300
50-
_/
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.^
^
*
^
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1
'^^"\^^
/
>
^
^^^^■^>C
^
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/
/
/
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-^DN'225'--
1 1 1 1
-><
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—
.„. ^z'^^^
"/
.J.
/^
-.
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/
/
/
^^
10'
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3
/
/
/
/
DN
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" p'^*<
-
"^
"^
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i^,^^^
/
DN 100-
^
>--.
^
'^
"
R -
^.1...
PiM an
VELOCITY
m/s)
.„..
■■
1
6 10 30 60 100
GRADIENT, (1 in ...)
(cl k = 0,6 mm
300 600 1000
1 u u u
......
•
~-
"
■^
._.
■
, ,
'^
^^^^..^^^ /
7
... ^ ._.
7' '"^"^
^
:;
/
/'
y
^^
7
>
-
/
/
-
—
f—
<
< 100-
/
/
3
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/
/
/
/
/
/
/
-■
2
/
"^
y
^— ^^^^
D
M i f^ n
i
.5-
_.
-
-
-
\
/
'1"
^;<;r; "
Zi
VELOCITY
1
PlM
1
D
(m/s)
u
Q
>
X
■
10-
10 30 60
GRADIENT. (1 in ...)
(d) k = 3.0 mm
1UU
300 600 1000
FIGURE 5.1 (in part) HYDRAULIC DESIGN CHARTS— WATER AT 20X
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67 AS/NZS 3500.3:2003
5.4.12 Design of surcharge outlets
5.4.12.1 General
Where the connection of any downpipes to the surface drainage system is not open to the
atmosphere and where a surcharge outlet will not affect the normal operation of the system,
at least one surcharge outlet shall be located along the site stormwater drain leading to a
point of connection. This surcharge outlet may also operate as an inlet pit or a grated drain.
Surcharge outlets shall be located —
(a) with the grate level —
(i) unless otherwise authorized by the network utility operator, not less than
300 mm below the lowest floor level; and
(ii) not less than 75 mm above an unpaved surface or level with a paved finished
surface;
(b) wholly within the property;
(c) clear of any buildings;
(d) so that any discharge is noticeable; and
(e) with an overflow path, so that overflows will not cause damage to buildings
(including contents) or danger to persons.
5.4.12.2 Design procedure
The procedure of the general method for design of a surcharge outlet shall be as follows:
(a) Determine the minimum area of the grated opening from the following equation:
^ Q ...5.4.12.2
150
where
A = the minimum grated area, in square metres
Q = the design flow of stormwater (assuming full blockage), in litres per
second
(b) Determine the exit velocity from the grated outlet and if greater than 0.15 m/s
increase the area of grate to achieve the determined exit velocity.
5.4.13 On-site stormwater detention (OSD) system
NOTE: A solution is not available for design of OSD systems because of sufficient data is not
available.
5.4.14 Concentrated discharges to streets
Where the network utility operator places a limit on the discharges that can be made to a
street gutter at a single point, the surface drainage system shall be altered if it is found that
the discharge exceeds such a limit. Alterations would usually involve the division of a pipe
system into two or more systems, discharging independently to the street (see
Clause 8.6.1.2(b)).
5.4.15 Snowfall effects
NOTE: In regions subject to snowfalls there is no special effect on the sizes of elements of
surface drainage systems, but precautions should be taken to minimize the entry of stormwater
run-off or meltwater into buildings or ponding against buildings as a result of accumulated snow.
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AS/NZS 3500.3:2003 68
5.5 NOMINAL METHOD
The 'nominal method' may be used for single dwellings in non-urban areas, and single
dwellings on urban allotments with less than 1000 m" in area. Pipe design shall be
determined according to local practice and experience (without specific design
calculations), and according to the minimum diameter (Clause 7.3.4), cover (Clause 7.2.6),
gradient (Clause 7.4.6) and other relevant criteria of this Standard.
The layout shall comply with Clause 5.3.
NOTES:
1 An example illustrating the application of the nominal method is given in Appendix K.
2 This method is suitable for two dwellings one above the other.
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69 AS/NZS 3500.3:2003
SECTION 6 SUBSOIL DRAINAGE S Y S T E M S —
D E S 1 G N
NOTES:
1 A method of design is outlined in Appendix M.
2 Detailed design of subsoil drainage systems are complex and dependent on particular site or
soil conditions. Such systems should be undertaken with advice from a suitably qualified
competent person. An example of a suitable qualified competent person is a professional
engineer specializing in geotechnieal engineering.
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70
SECTION 7 SURFACE AND SUBSOIL
DRAINAGE S Y S T E M S — 1 N S T A L L A T I O N
7.1 SCOPE OF SECTION
This Section specifies installation requirements for site stormwater drains for conveyance
of stormwater from roof and surface (see Clause 7.2, as applicable, and Clause 7.3), and
subsoil drainage systems (see Clause 7.2, as applicable, and Clause 7.4).
7.2 GENERAL REQUIREMENTS
7.2.1 Products and joints
Products and joints for site stormwater drains and subsoil drains shall comply with
Section 2 and Clause 4.15.
7.2.2 Erosion and sediment controls
During construction appropriate precautions to minimize soil erosion and the escape of
sediment from the site due to rainfall and stormwater should be considered. These
precautions may include —
(a) covering exposed or disturbed surfaces with vegetation or meshes to prevent erosion
and mobilization of sediments;
(b) surface grading of sites and the direction of stormwater flow paths through
construction sites so that erosion is minimized, including limits on slopes and
lengthening of flow paths using barriers;
(c) provision of sediment barriers along flow paths and watercourses, such as silt fences,
hay bales and porous stone filters; and
(d) construction of temporary sediment traps or basins (usually near site boundaries) to
collect sediments for removal.
7.2.3 Terminology
Trench terminology for flexible and rigid pipes is shown in Figure 7.1.
Finished surface
Trench fill -
Existing surface
Trench wall
Overlay^
Embedment
Haunch support
i
Bedding
Side
support
^^M Foundation ^^^
(a) Flexible pipes
Finished surface-
Trench fill - — -
Existing surface-
Trench wall -—
Overlay!
Embedment
Haunch support
Bedding
(b) Rigid pipes
FIGURE 7.1 TRENCH TERMINOLOGY
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71 AS/NZS 3500.3:2003
7.2.4 Trench width
Trench widths measured at the top of the pipes, between the faces of either the unsupported
trench walls or the inside face of the sheeting of the trench support system, shall be not less
than the widths specified in —
(a) AS 1762, for corrugated metal pipes;
(b) AS/NZS 2566. 1 , for flexible pipes and fittings;
(c) AS 3725, for FRC and reinforced concrete pipes; and
(d) AS 4060, for vitrified clay and ceramic pipes and fittings.
7.2.5 Over-excavation
Where a trench has been excavated deeper than necessary, the excess depth shall be filled
either with bedding material compacted to achieve a density as near to the original soil
density as possible, or with concrete.
7.2.6 Cover
Except as specified in Clause 7.3.7, the cover shall be not less than that given in Table 7.1
or shall be in accordance with —
(a) AS 1762, for corrugated metal pipes;
(b) AS 2032, for PVC pipes;
(c) AS/NZS 2566.1, for flexible pipes and fittings;
(d) AS 3725, for reinforced concrete and FRC pipes;
(e) AS 4060, for vitrified clay and ceramic pipes and fittings; and
(f) AS 2033, for polyethylene pipes
7.2.7 Proximity to other services
Above and below ground site storm water drains shall be installed as follows:
NOTE; The proximity to other services will vary, depending on the type and size of the services
affected.
(a) No potential safety hazard shall be created when in close proximity to other services.
(b) Access for maintenance and potential branch insertions shall not be impaired by other
services.
(c) Sites shall not be located where physical damage to the drain is likely to occur, unless
adequate protection is provided.
(d) Separation from above-ground electrical conduit, wire, cable, consumer gas pipes or
water service shall be at least 100 mm between any downpipe.
(e) Stormwater drains shall not be installed in below ground situations where electrical
supply cables, consumer gas piping, water service or communications
cable are intended to be installed below ground in the area above the drain.
(f) The separation between any underground stormwater drain and an electrical supply
cable shall be at least —
(i) 100 mm provided the electrical supply cable is indicated along its length with
orange marker tape complying with AS/NZS 2648.1 and is mechanically
protected; or
(ii) 600 mm where the electrical supply cable is neither indicated nor mechanically
protected.
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AS/INZS 3500.3:2003 72
(g) The separation between any underground stormwater drain and consumer gas pipes
shall be at least—
(i) 100 mm provided the consumer gas pipe is indicated along its length with
marker tape complying with AS/NZS 2648 J laid 150 mm above the installed
pipe; or
(ii) 600 mm where the consumer gas pipe is neither indicated nor mechanically
protected.
MOTE: Mechanical protection is provided by concrete slabs, continuous concrete pour,
or bricks designed for protecting electrical supply cables.
(h) The separation between any underground stormwater drain and an electrical earthing
electrode, for an electrical supply not exceeding 1000 V, shall be at least 600 mm.
For an electrical supply exceeding 1000 V, the relevant regulatory authority shall be
contacted for a ruling.
(i) The separation between any underground drain and a communication cable shall be at
least 100 mm.
(j) The separation between any underground stormwater drain and any other service
other than consumer gas piping and electrical or communication service shall be at
least —
(i) 100 mm from a drain not exceeding DN 100 and is serving the same property;
and
(ii) 300 mm for any other service exceeding DN 100.
(k) Any underground stormwater drain crossing another service shall —
(i) cross at an angle of not less than 45° (see Figure 7.2);
(ii) have a vertical separation of not less than 100 mm; and
(iii) be marked along its length for 1 m either side of the centreline of the service
with marker tape complying with AS/NZS 2648.1, laid 150 mm above the
installed service.
Crossover
Original service
FIGURE 7.2 PERMITTED CROSSOVER ZONE FOR ELECTRICAL CABLES AND GAS
PIPES
(I) Stormwater drains shall be installed with sufficient clearance to any underground
obstruction to protect the drain from physical damage and to permit repairs. The
clearance shall be at least 300 mm.
NOTE: See Clause 7.2.9 for drains in close proximity to footings or foundations.
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AS/NZS 3500.3:2003
TABLE 7.1
MINIMUM PIPE COVER
(from finished surface to top of pipe)
inilhinetres
Location
Cast iron, ductile
iron, galvanized steel
Other authorized*
products
Minimum cover
1 T^ot
subject to vehicular loading:
(a)
without pavement—
(i) for singie dwellings
Nil
100
(ii) for other than Item (i)
Nil
300
(b)
with pavement oi^ brick or unreinforced
concrete
Nilt
501-
2 Sub
ect to vehicular loading;
(a)
other than roads —
(i) without pavement
3Q0
450
(ii) with pavement of^
(A) reinl^orced concrete for heavy
vehicular loading
NiltJ
lOOtt
(B) brick or unreinforced
concrete for light vehicular
loading
NiltJ
75tJ
(b)
roads —
(i) sealed
300
500J
(ii) unsealed
300
500:1:
3 Sl
in
bject to construction equipment loading or
embankment conditions
300
500}
* Includes overlay above the top of the pipe of not less than 50 mm thick.
t Below the underside of the pavement.
} Subject to compliance with AS 1762, AS 2033, AS/NZS 2566.1, AS 3725 or AS 4060.
7.2.8 Shoring and underpinning buildings
Where the bottom of the trench is adjacent to or below the footing and walls of any
adjoining building or structure, the footing shall be adequately supported while the trench is
open.
NOTE: Criteria for the footing support and backfilling of the trench should be determined by a
professional engineer.
7.2.9 Installation near and under buildings
A drain in close proximity to footings or foundations shall comply with the following:
(a) Where the drain passes under a strip footing, its angle of intersection with the footing
in the horizontal plane shall not be less than 45°, and the minimum clearance between
the top of the drain to the underside of the footing shall be 25 mm.
(b) If the drain is laid through footings or walls, other than below ground, external walls,
it shall be installed with an annular space of not less than 25 mm filled with a liner of
flexible material.
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74
(c) The drain may be laid through below ground external walls, provided that —
(i) two flexible joints are provided externally within 800 mm of the external face
of the wall, and such joints are not less than 600 mm apart; and
(ii) the penetration of the wall is made watertight.
(d) Where the drain is to be laid parallel to a footing, the trench shall be located —
(i) in Australia —
(A) in accordance with the Housing Provisions of the BCA Clause 3.1 .2.2(d);
(B) for single dwellings, as shown in Figure 7,3; and
(C) for all others, as determined by a suitably qualified competent person; or
(ii) in New Zealand, as specified in EI/ASl .
(e) Criteria for pile systems shall be determined by a suitable qualified competent person.
A2
/ 1
-^^^ — ^
Existing surface
■Finished surface
imm
Depth to
bottom o
trench
(varies
mmmmmm~
Floor slab
J^ — 'm^m^
H
Soil type
Slope W;L
Compacted fill
Undisturbed ground
Stable rock (*)
Sand n
Silt (t)
2:3
1:2
1:4
8:1
1:2
1:4
Firm clay
Soft clay
Soft soils (t)
1:2
Not suitable
Not suitable
1:1
2:3
Not suitable
* Most sand and rock sites with little or no ground movement from moisture
changes.
t Sites include soft soils, such as soft clay or silt or loose sands; landslip; mine
subsidence; collapsing soils; soils subject to erosion; reactive sites subject to
abnormal moisture conditions or sites which cannot be classified otherwise.
NOriZ: This Table has been adapted from the 13CA Housing Provisions and users of this
Standard should satisfy themselves that the Table is still relevant and has not been
amended.
FIGURE 7.3 EXCAVATION NEAR FOOTINGS
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75 AS/NZS 3500.3:2003
7.2.10 Water-charged ground
Excavation in water-charged ground shall be in accordance with the following:
(a) The water level shall be lowered below the bottom of the proposed trench and
maintained at that level during construction, including the placing of trench fill.
(b) Dewatering shall be carried out by pumps and spearheads or similar devices. The
removed water shall discharge to a location where it shall not cause a nuisance or
damage, and in no case shall it discharge, either directly or indirectly, into any
sanitary sewer.
MOTE: Where water-charged ground is encountered, consideration needs to be given to the effect
on adjacent buildings and other services.
7.2.11 Other than stable grounds
Unless otherwise authorized by the network utility operator, where excessive soil
movement due to filled, unstable or water-charged ground may affect the performance of
any site stormwater drain or subsoil drain, then such drain shall be installed in accordance
with the plans and specification, based on a geotechnical report and calculations, prepared
by a suitably qualified competent person.
NOTE: In proclaimed mine subsidence districts, site stormwater drains larger than DN 225 should
comply with the requirements of the relevant authority.
7.2.12 Trench fill
Trench fill shall either —
(a) be material excavated from the trench or imported, provided that the material placed
within 300 mm of the top of pipes is free from builders' waste, bricks, pieces of
concrete, rocks or similar material that would be retained on a 75 mm sieve; or
(b) be embedment material (see Clause 7.3.6).
7.2.13 Backfilling
Trench fill shall be placed in loose layers not more than 200 mm thick and compacted to not
less than 90% or 95% under pavements of the standard maximum dry density specified in
AS 1289.5.4.1 or AS I289.E6.1, in such a way that the pipes are neither dislodged nor
damaged.
The finished surface (top of trench fill) and the trench surround shall be restored, as near as
practicable, to the level and condition of the existing surface before commencement of the
excavation (see Figure 7.1).
7.2.14 Excavation near point of connection
Excavation by a machine shall not be carried out within 600 mm of a point of connection to
an external stormwater drainage network,
7.3 SITE STORMWATER DRAINS
7,3,1 Corrosive areas
Buried metal pipes and fittings in corrosive areas shall be externally protected by—
(a) an external protective coating (see Clause 2.13.4);
(b) sealed polyethylene sleeving (see Clause 2.13.7); or
(c) continuous wrapping with petrolatum taping material.
NOTE: Corrosive areas contain compounds consisting of magnesium oxychloride (magnesite) or
its equivalent, coal wash, sodium chloride (salt), ammonia or materials that may be detrimental to
the installation.
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76
7.3.2 General
7.3.2.1 Site stormwaler drains
(a) Site stormwater drains shall be laid —
(i) with no lipped joints or internal projections;
(ii) so as to prevent the ingress of embedment and trench fill, or embankment fill;
(iii) with protection, as required, to prevent damage during installation and service;
and
(iv) using sweep junctions.
7.3.2.2 Site stormwater pipes
Pipes for site stormwater drains shall —
(a) have joints that comply, where appropriate, with Clauses 2.8 and 4.1 5;
(b) where installed below ground, for other than cast iron, ductile iron and galvanized
steel, be continuously supported by embedment (see Clause 7.3.6);
(c) where installed above ground, have support systems authorized by the network utility
operator; and
(d) be cleaned internally prior to installation and commissioning.
7.3.3 Connections to pits and arresters
Where a site stormwater drain passes through the wall of a pit or arrester that is more than
1 m deep, two flexible joints shall be located on such drain within 800 mm of the outer face
of the structure, and not more than 600 mm apart.
7.3.4 Minimum diameter
Minimum diameters —
(a) for single dwellings in rural areas, and residential buildings on urban allotments with
areas less than 1000 m^ shall be DN 90; and
(b) for other properties, downstream of a stormwater or inlet pit, shall be the greater of —
(i) the diameter of the largest pipe entering the pit; or
(ii) DN 150.
An exception to this is at footpath crossings (see Clause 8.6.1 .2(b)) where multiple pipes of
DN 100 or less may be used.
7.3.5 Gradients
The minimum gradient of a site stormwater drain shall be as given in Table 7.2. No
maximum gradient is specified, but designers should be aware of the possibility of scour of
pipes by rapid Hows, particularly by sediment-laden water.
TABLE 7.2
MINIMUM GRADIENT OF SITE STORMWATER DRAINS
Nominal
size
Miniinuin gradient
Nominal
size
IMinimum gradient
DN
Aust.
NZ
ON
Aust.
NZ
90
100
150
1:100
1 : 1 00
1:100
1:90
1:120
1 :200
225
300
375
1 :200
1:250
1:300
1:350
1:350
1:350
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77 AS/NZS 3500.3:2003
7.3.6 Embedment
7.3.6.1 Materials
Embedment material shall comply with the following:
(a) Pipes shall be as specified in —
(i) AS 1762, for corrugated metal pipes;
(ii) AS 2032, for PVC pipes;
(iii) AS 2033, for polyethylene pipes;
(iv) AS/NZS 2566.1, for flexible pipes and fittings;
(v) AS 3725, for FRC and reinforced concrete pipes; and
(vi) AS 4060, for vitrified clay and ceramic pipes and fittings; and
(b) All other authorized pipe materials:
(i) Bedding material shall be —
(A) suitable sand, free from rock or other hard or sharp objects that would be
retained on a 13.2 mm sieve;
(B) crushed rock or gravel up to a maximum size of 14 mm;
(C) excavated material, provided that this is free from rock or hard matter,
and is broken up so that it contains no soil lumps having any dimension
greater than 75 mm; or
(D) cement mortar containing one part of portland cement and four parts of
sand by volume thoroughly mixed with clean water to a workable
consistency.
(ii) Side support and overlay material shall comply with Item (b)(i), (A), (B), or
(C).
7.3.6.2 Installation
Embedment shall be installed so that a site stormwater drain is neither dislodged nor
damaged, and in accordance with the following:
(a) AS 1 762, for corrugated metal pipes,
(b) AS 2032, for PVC pipes,
(c) AS/NZS 2566. 1 , for flexible pipes and fittings.
(d) AS 3725, for FRC and reinforced concrete pipes.
(e) AS 4060, for vitrified clay and ceramic pipes and fittings.
(f) All other authorized materials shall be as follows:
(i) The pipe class shall comply with Section 2.
(ii) The foundation shall be consistent and excavated to the gradient and, where
over excavated, shall comply with Clause 7.2.5.
(iii) The bedding material shall be one of the following:
(A) Cement mortar, as specified in Clause 7.3,6.1 (b)(i)(D), where the trench
foundation is rock or shale and the gradient is steeper than 1:5 and
shall—
(1) be a minimum depth of 50 mm measured below the bottom of the
pipe;
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AS/NZS 3500.3:2003 78
(2) be not ]ess than 75 mm wide;
(3) be kept clear of flexible joints; and
(4) have pipes supported at distances not greater than 1.5 m from the
centres of support, prior to placing the mortar bedding; or
(B) Earth foundations not less than 75 mm thick.
(C) Rock foundations not less than 100 mm thick with the haunch support not
less than 75 mm thick (see Figure 7,1).
NOTE: Cast iron and ductile iron pipes may be unsupported for up to 600 mm
either side of each pipe joint.
(iv) Chases shall be excavated in the bedding and, if necessary, in the foundation to
prevent sockets bearing on either, while pipe lengths shall be fully supported
within 600 mm of each socket.
(v) The embedment material specified in Clause 7.3.6. l(b)(i) Items (A) to (C) shall
be placed in loose layers not more than 200 mm thick and compacted to 90% of
the standard maximum dry density as specified in AS 1289.5.4.1 or
AS ]289.E6.1.
7.3.7 Cover under buildings
For site stormwater drains under buildings —
(a) the thickness of overlay between the top of the pipe and the underside of a reinforced
concrete slab shall be not less than 25 mm; and
(b) there shall be adequate protection from mechanical damage,
7.3.8 In easements and public places
7.3.8.1 General requiremenis
A site stormwater drain located in a road, easement, public place, right of way or the like in
an open-cut trench, shall be installed in accordance with the following:
(a) Where the full depth at the point of connection is not required to drain the property, a
jump-up (see Clause 8.9) shall be installed either at the point of connection, or within
the property boundary.
(b) Where the presence of any conduit or pit prevents the site stormwater drain from
being laid at an even grade with the required cover, then wherever practicable the
drain shall pass beneath the conduit or pit at an even grade with a Jump-up permitted
only at the point of connection. If this is not practicable —
(i) an inclined section of pipe may be installed adjacent to the conduit or pit, in the
form of a graded jump-up with changes of direction not greater than 60° in the
vertical plane; and
(ii) there shall be a minimum clearance of 25 mm between the conduit or pit and
the drain.
(c) The site stormwater drain shall have a minimum cover as specified in Clause 7.2.6.
(d) A site stormwater drain, located in a public road or right-of-way shall have no fitting,
which is part of a stormwater drainage system, installed above the level of a finished
surface.
7.3.9 Disconnection
Where a disused site stormwater drain is to be disconnected, the following criteria apply:
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79 AS/NZS 3500.3:2003
(a) Where the disconnection is in water-charged ground, dewatering shall be carried out
in accordance with Clause 7.2.10.
(b) Disconnection shall be made at either the point of connection to the external
stormwater drainage network or the connection to the works remaining.
(c) Extraneous water, soil, sand, rock or other substances shall not be permitted to enter
the site stormwater drain or external stormwater drainage network downstream of the
disconnected section.
(d) Site stormwater drains shall be made watertight using a cap or plug, and sealed in a
manner appropriate to the material remaining in use.
7.3.10 Testing
Site stormwater drains, drains within and under buildings and main internal drains shall
comply with Section 10.
7.4 SUBSOIL DRAINS
7.4.1 General
Subsoil drains shall be laid —
(a) so any pipe or geocomposite drain employed can be flushed out;
(b) with protection to prevent damage; and
(c) with clean-out points for pipes or geocomposite drains —
(i) located at —
(A) their topmost ends (or heads); and
(B) each change of direction greater than 70°; and
(ii) constructed so that they —
(A) intersect the drain at an angle not greater than 45°;
(B) extend vertically to the top of paved surfaces or within 300 mm of an
unpaved finished surface; and
(C) terminate with a screw cap legibly marked 'SW.
Any pipes and fittings in such drains shall be —
(1) cleaned internally prior to installation and commissioning;
(2) continuously supported by embedment (see Clause 7.3.6); and
(3) appropriately jointed where applicable.
NOTES:
1 Installation of subsoil drains may include —
(a) wrapping of the pipes or geocomposite drains with geotextile material prior to
placement of the embedment;
(b) wrapping of all or part of the embedment with geotextile material; or
(c) other methods authorized by the regulatory authority.
2 Joint overlaps for geotextile material should not be less than 300 mm.
7.4.2 Embedment
7.4.2.1 Materials
The material for bedding, haunch support, side support and overlay is determined by —
(a) the characteristics of the ground in which the subsoil drain is located;
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AS/NZS 3500.3:2003 80
(b) the type of geotextile material used (if applicable).
Where the conduit consists of a pipe, the embedment material shall be crushed hard rock or
natural gravel with not less than 90% by mass retained on a 9.5 mm sieve. Where the
conduit is a geocomposite drain the material may be a coarse washed sand.
Criteria for sizing and determining arrangements of filter material are as follows:
(i) For proper performance, the filter material (or backfill) shall surround the drain,
under as well as over; however, this will depend on the nature of the strata being
drained and the depth of drain.
If a drain penetrates a water-bearing layer, and is socketed into an impervious zone
below, then the filter material shall as a minimum be placed in contact with the
pervious soil. A suitable pipe bedding material may surround the pipe.
If a drain only partially penetrates a pervious layer such that water would be expected
to flow into a drain over its entire depth, then the filter material shall surround the
pipe and also to act as the pipe bedding material.
(ii) Where pipe bedding is a different material to the filter material, it shall be coarser
grained than the filter material and its particles have to be greater in size than the
perforations in the pipe unless a geotextile wrapping is provided. Ideally, the grain
size distribution of the bedding material should be chosen so that it itself acts as a
filter to the filter zone.
MOTE: Common practice is to choose a free-draining, stable and inert material with a larger
grain size than the filter, such as good quality, screened, crushed rock.
(iii) A coarse washed sand should be used as a backfill when geocomposite subsurface
drains are used. The coarse sand acts as the primary filter and the geotextile wrap on
the drain as a secondary filter.
7.4.2.2 Installalion
Subsoil drains shall be laid—
(a) with embedment installed so that a subsoil drain is neither dislodged nor damaged;
and
(b) so as to prevent the ingress of embedment and trench fill.
7.4.2.3 Disconnection
Disused subsoil drains shall be disconnected in accordance with the following:
(a) A subsoil drain shall only be disconnected if it has been established that it is not in
use or that it is no longer required to serve its intended purpose.
NOTE: Where there is any doubt as to its purpose or the effects of disconnection, expert
geotechnical advice should be sought.
(b) A disconnection shall be made at a pit or other connection to a site stormwater drain.
(c) Extraneous water, soil, sand, rock or other substances shall not be permitted to enter
the site stormwater drain or external stormwater drainage system downstream of the
disconnected section.
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SECTION 8 SURFACE AND SUBSOIL
DRAINAGE S Y S T E M S — A N C I L L A R I E S
8.1 SCOPE OF SECTION
This Section specifies criteria for ancillaries of surface and subsoil drainage systems.
8.2 PAVED SURFACES
Gradients for paved surfaces with areas exceeding 200 m , which form part of a surface
drainage system in accordance with Clause 5.2. 1 (a), (b) or (c), are given in Table 8.1.
TABLE 8.1
TYPICAL GRADIENT LIMITS FOR PAVED AREAS
Drained area
Gradient
Access roads
Paved areas
Footpaths
Longitudinal gradient or fall
1:10 max.*
—
—
Road crossfall or average camber
1 :40 normal
1 :60 min.
1:30 max.
1:40 min.
Kerb channels:
(without concrete gutter)
(with concrete gutter or high -class
surfacing)
1:150 min.
1:200 min.
1:150 min.
1:200 min.
—
Superelevation for road curves not
exceeding 100 m radius
1 :25 max.
—
—
* The first 10 m of an access road from its Junction with a major road or public highway should
have a gradient of not more than 1 :30.
NOTFE: Except for longitudinal gradient or fail, the typical gradient limits are taken from BS 6367.
8.3 POINT(S) OF CONNECTION
NOTE: See Clause 1.7.1 for criteria.
8.4 REFLUX VALVES
8.4.1 Purpose
Reflux or non-return valves allow flow in one direction only, permitting storm water to flow
from a property but preventing backflows due to surcharging of the downstream stormwater
drainage network.
8.4.2 Location
Reflux valves and reflux valve chambers shall be located —
(a) wholly within the property; and
(b) in a stormwater pit unless such valve is —
(i) above the finished surface level and can be maintained from this level; or
(ii) within a building and accessible with clear space above so that it may be
maintained.
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8.4,3 Criteria
A reflux valve shall be installed —
(a) where the network utility operator has determined a surcharge level at a gravitational
point of connection that is above —
(i) any floor or basement level; or
(ii) if appropriate, any paved or unpaved area; or
(b) where the surcharge outlet is omitted.
8.5 INSPECTION OPENINGS
8.5.1 Location
For other than single dwellings, inspection openings for the maintenance of site stormwater
drains shall be extended to and capped at the finished surface level and be installed at —
(a) each point of connection;
(b) even spacings not more than 30 m apart;
(c) each end of any inclined jump-up that exceeds 6 m in length;
(d) each connection to an existing site stormwater drain; and
(e) at any change of direction greater than 45°.
Inspection openings may be replaced by an inlet or stormwater pit.
8.5.2 Size
The nominal size of inspection openings for site stormwater drains shall be —
(a) for nominal pipe sizes less than or equal to DN 150, the same size as the site
stormwater drain; and
(b) for nominal pipe sizes greater than DN 150, not less than DN I 50.
8.5.3 Access
Access to below-ground inspection openings shall be either by —
(a) a stormwater pit; or
(b) a sealed riser terminated at ground level or floor level in an accessible position.
8.5.4 Plugs or caps
Inspection openings and unused sockets shall be sealed with airtight removable plugs or
caps fitted with an elastomeric seal and securely held in position by a clip, strap or threaded
connection. Each plug or cap shall be legibly marked 'SW.
When a plug or cap with an elastomeric seal is removed, a new seal shall be fitted before it
is replaced.
8.6 STORMWATER PITS, INLET PITS AND ARRESTERS
8.6.1 Purpose
8.6,1.1 Slonnwaler pits
Stormwater pits are installed —
(a) to provide access to and, where appropriate, maintenance of—
(i) junctions, changes of gradient and changes of direction of site stormwater
drains;
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(ii) inspection openings within buildings;
(iii) reflux valves; or
(iv) flap valves fitted at the downstream ends of subsoil drains; and
(b) where appropriate, to operate as an inlet pit.
8.6 J. 2 Inlet pits
Inlet pits are installed —
(a) to permit the collection and ingress of stormwater to a site stormwater drain.
(b) where necessary, to operate as a surcharge outlet (see Clause 5.4. 12); or
(c) when the point of connection is a street kerb and gutter and the diameter of the site
stormwater drain is larger than DM 100,
NOTE: A sump and screen similar to that shown in Figure 8.1 should be provided adjacent to the
property boundary to provide transition to smaller pipes or conduits passing under the footpath.
Larger than
DN 100
Property boundary
Mesh and screen
(optional)
Multiple DN 75 or
DN 100 pipes or
rectangular conduits
FIGURE 8.1 TYPICAL ARRANGEMENT OF INLET PIT AND FOOTPATH CROSSING
8.6.1.3 Arresters
Arresters shall be installed to remove contamination, generally silt, oil, or both, from
stormwater prior to discharge to the stormwater drainage network.
8.6.2 Size
8.6.2.1 Stormwater and inlet pits
Minimum internal dimensions for stormwater and inlet pits are given in Table 8.2.
TABLE 8,2
MINIMUM INTERNAL DIMENSIONS FOR
STORMWATER AND INLET PITS
Depth to invert
of outlet
Minimum internal dimensions
mm
Rectangular
Circular
Width
Length
Diameter
<6()0
>6()() <90()
>90() <12()()
> 1 200
450
600
600
900
450
600
900
900
600
900
1 000
1 000
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8.6.2.2 Arresters
The minimum internal dimensions and spacings for baffles and weirs for —
(a) silt arresters shall be as shown in Figure 8,2; and
(b) general purpose (oil or silt, or both) arresters shall be as shown in Figure 8.3.
Removable lid-
Existing surface
Inlet
-50 mm
Water level
F7^^^
— y Outlet
i^-
'. •• .';• "•* *-■
millimetres
Minimum Internal dimensions
Nominal size of
outlet
DN
Rectangular
Circular
Depth below invert
Width
Length
Diameter
of outlet
<150
225
300
375
600
700
800
1 000
1 000
1 000
1 000
1 200
1000
1000
1000
1200
450
450
450
550
FIGURE 8.2 MINIMUM INTERNAL DIMENSIONS FOR SILT ARRESTERS
8.6.3 Falls across pits
The positions of inlet and outlet pipes for pits in site stormwater drains shall be selected to
minimize head losses, and to facilitate the flushing of sediment from pits. The following
criteria apply:
(a) Where possible, inlet pipes shall be pointed directly at the pit outlet, to assist the
passage of flow and reduce turbulence,
(b) Pits without a sump, as shown in Figure 8.4(a), shall have the floor graded to fall at
least 20 mm between the inverts of the inlet and outlet pipes. Sump pits shall have a
flat floor, but a fall of at least 20 mm between pipe inverts, as shown in Figure 8.4(b).
8.6.4 Inlets
Gratings or slotted kerb inlets of sufficient size to admit the flows shall be provided, as
specified in Clause 5.4.10, Where pits act as surcharge outlets, the provisions of
Clause 5.4. 12 shall apply.
For concrete paved areas care should be taken that construction or expansion joints do not
coincide with the lines of collecting channels and do not cross areas in which ponding
occurs at sag inlets. Gratings shall be set 5 mm below the levels of surrounding paved areas
to allow for settlement af\er construction.
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Frames of gratings or inspection covers on pits in areas subject to vehicular traffic shall be
bedded using good quality mortar with low-water content on well-built masonry or concrete
walls. Sufficient time shall be allowed for the bedding to develop its strength before a
grating or cover is subjected to traffic.
-Lid — 3 sections with
inspection opening
Slot tor
battles 5 0--H ^-
/ Litting holes grouted up
atter installation
each end
Inlet
4
150
-r
300
4- -^
150
Baffle No. 1
Platform
450
-^
r™-P- 4oH
" " "" ~T
Baffle No. 2
r
300
L
'-Existing
surface
Typical sectional view
millimetres
Maximum
hourly
discharge
L
Minimum internal dimensions
Minimum spacing of baffles and weir
Width
Length
Depth
below
crest of
weir
Inlet to
baffle
No. 1
Baffle No. 1
to baffle No. 2
Baffle No.
2 to weir
Weir to
outlet
500
750
1 000
1 500
2 000
3 000
4 000
5 000
600
600
700
700
1 000
1 250
1 350
1 450
1 870
1 870
2 660
3 020
3 020
3 820
4 020
4 020
700
1 000
600
600
780
1 050
1 150
1 250
200
200
300
300
300
300
300
300
1 200
1 200
1 640
2 000
2 000
2 500
2 700
2 900
150
150
300
300
300
300
300
300
200
200
300
300
300
600
600
600
DIMENSIONS IN MILLIMETRES
FIGURE 8.3 TYPICAL MINIMUM DIMENSIONS FOR GENERAL PURPOSE
(OIL OR SILT OR BOTH) ARRESTERS
Inlet pipe
Fall ^20 mm
Outlet pipe
Inlet pipe
Fall ^20 mm--
Outlet pipe
(a) Pit without sump (b) Sump pit
FIGURE 8.4 REARRANGEMENTS
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8.6.5 Materials and construction
8.6.5.1 Rectangular or square pits and arresters
Rectangular or square stormwater pits and inlet pits and all arresters shall be either one of
the following:
(a) Constructed in situ on a concrete bed with at least the same external dimensions as
the pit or arrester and at least 1 50 mm thick with walls of —
(i) brickwork for wall depths, measured from the existing surface to the invert of
the outlet, that —
(A) do not exceed 600 mm, at least 1 1 mm thick; or
(B) exceed 600 mm but not 1 500 mm, at least 230 mm thick;
(ii) non-reinforced concrete with thickness not less than that determined from
Figure 8.5; or
(iii) reinforced concrete with thickness and reinforcement determined by a
professional engineer.
(b) Precast or prefabricated in accordance with Clause 2.13,8.
8.6.5.2 Circular pits
Circular stormwater pits and inlet pits shall be pre-cast or prefabricated in accordance with
Clause 2. 12.8.
8.6.5.3 Conduits and channels
The conduits and channels in pits shall be constructed in accordance with the following:
(a) The fall from the invert of each inlet to the invert of the outlet shall not be less than
the values given in Figure 8,4.
(b) For pits located inside buildings, Hows shall be conveyed through the pit by —
(i) a fully enclosed conduit with sealed inspection openings; or
(ii) a graded floor, with the pit fitted with an airtight cover.
(c) For pits located outside buildings, flows shall be conveyed through the pit —
(i) as specified for Item (b)(i); or
(ii) by a graded floor or sump.
Inlet pits in locations subject to dengue fever borne by mosquitoes shall be without a sump
and be self-draining.
8.6.5.4 Ladders
Rung and individual-rung ladders installed in pits and arresters shall comply with AS 4198
and AS 1657, respectively.
Following manufacture, steel ladders shall be hot dip zinc galvanized as specified in
AS/NZS 4680.
8.6.5.5 Cement rendering
Brick walls and floors of pits and arresters shall be rendered with a coat of cement mortar at
least 10 mm thick, trowelled to a smooth finish.
8.6.5.6 Upper Myalls of stormwater pits
The upper walls of stormwater pits shall be —
(a) vertical; or
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(b) tapered upwards to the access shaft from a point not less than —
(i) 1 500 mm above the invert of the outlet pipe; and
(ii) 100 mm above the top of the highest inlet pipe.
The diameter of the access shaft shall be not less than 600 mm, and its length shall be not
greater than 350 mm.
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LU
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6.0
5.4
4.8
4.2
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3.0
2.7
2.4
2.1
1.8
1.5
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(b) Section A-A
0.45 0.6 0.9 1.2 1.5
LENGTH OF WALL [L], METRES
(a) Value of wall thickness T^ or 72
T
Plan
Example;
For a non-reinforced concrete wall of length [L] ~ 1.2 m, and maximum depths of 1.8 m
[H-]] and 2.4 m {H2) the thicknesses are 175 mm [T-]) and 200 mm {T2], respectively.
NOTB: Thickness T2 obtained from the graph applies to the thickness ol^the bottom section, and 11 to the top
section.
FIGURE 8.5 MINIMUM THICKNESS OF NON-REINFORCED CONCRETE WALLS FOR
PITS AND SILT ARRESTERS
8.6.5.7 Access openings
Stormwater pits that are not intended to act as inlets for stormwater and for arresters,
circular or rectangular access openings shall be fitted at finished surfaces with removable
covers with a clear opening of not less than 500 mm.
8.6.5.8 Construction joints
Construction joints shall be made in accordance with the following:
(a) Not more than 24 h shall elapse between successive pours of concrete.
(b) The keying surface shall be scabbled and cleaned.
(c) A thick cement slurry shall be applied immediately prior to pouring concrete.
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8.6.5.9 Inserts
Holes broken in or formed in walls of pits and arresters for insertion of pipes or fittings
shall be made watertight by —
(a) keying and preparing as for construction joints and caulking the annular space
between the concrete and pipe or fitting w^ith a stiff mortar (see Clause 2. 10.5); or
(b) sealing with an epoxy-based or other sealant authorized by the network utility
operator.
8.6.5.10 Connections
Connections to pits and arrestors shall comply with Clause 7.3.3.
8.7 SURCHARGE OUTLETS
Surcharge outlets shall comply with Clause 5.4.12.
8.8 JUNCTIONS
8.8.1 General
Junctions in site storm water drains shall be made by means of —
(a) an oblique junction or sweep junction at an upstream angle of not greater than 60°, as
shown in Figure 8.6, and preferably less than 45°;
(b) an opening cut into a site stormwater drain in accordance with Figure 8.7 for nominal
pipe sizes equal to or greater than DN 375; or
(c) a pit.
FIGURE 8.6 ALLOWABLE OBLIQUE OR SWEEP JUNCTION CONNECTION
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Main
Elastomeric sea!
C£ branch
"^"Gradient (see Clause 7.3.5)
Angle to suit gradient
of branch line 45** max,
Inside of joint to be
filled with mortar and ^^-- ^ ^^ '--Wire netting reinforcement
wiped smooth all round
"^--Mass concrete block for nominal
sizes greater than DN 150
NOTES:
1 Ihe centre-line of each branch shall intersect the centre-line of the main line.
2 The change of direction of (low at a cut-in shall be between 45° and 90°, as shown in Figure 8.8.
DIMENSIONS IN MILLIMETRES
FIGURE 8.7 CUT-IN CONNECTION FOR SITE STORMWATER DRAINS EQUAL TO OR
GREATER THAN DN 375
FIGURE 8.8 ALLOWABLE CHANGE OF DIRECTION OF FLOW AT A BRANCH
CONNECTION OR CUT-IN
8.8.2 Square junctions
For site stormwater drains square junctions shall only be used —
(a) at the top of a jump-up at a point of connection;
(b) as an inspection opening; or
(c) at the top of a jump-up in the site stormwater drain in lieu of a bend and inspection
opening.
8,9 JUMP-UPS
Jump-ups in site stormwater drains shall be constructed in accordance with the following:
(a) The bend at the base of the jump-up shall be supported on a concrete footing of a
thickness not less than 100 mm and extending upwards not less than 100 mm.
(b) Either a bend incorporating a full-size inspection opening or a junction fitting shall be
used at the top of the jump-up (see Figure 8.9).
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(c) Branch site stormwater drains shall connect to the shaft of a jump-up using junction
fittings shown in Figure 8.9 and shall be fully supported.
(d) The jump-up shall be protected and supported during installation and placement of
trench fill.
8.10 ANCHOR BLOCKS
Where the gradient of a site stormwater drain exceeds 1:5, anchor blocks shall be
installed —
(a) at the bend or junction at the top and bottom of the inclined site stormwater drain (see
Figure 8,10); and
(b) at intervals not exceeding 3 m.
Anchor blocks for such drains shall be of reinforced concrete —
(i) with a thickness of not less than 1 50 mm;
(ii) with steel reinforcement for such drains of nominal sizes —
(A) DN 100 or DN 150, two bars of not less than 10 mm diameter bent to a radius
of about 200 mm or 250 mm, respectively and placed as shown in Figure 8.10.
(B) greater than DN 150, shall be designed by a suitably qualified competent
person;
(iii) which extends —
(i) across the full width and is firmly keyed into the sides of the trench;
(ii) above the top of such drain by not less than 1 50 mm; and
(iii) below the foundation of the trench by not less than 150 mm; and
(iv) which does not cover any flexible joint.
Finished surface x ^-Existing surface
'W^^M^
a
n-^^^^
60 mm max. -• »- Z
w,
m
4><
yy/yy///
V
■//////
Hardwood struts
^)
.--—Oblique or swept junction
^^-— Concrete
FIGURE 8.9 VERTICAL JUMP-UP TO BRANCH SITE STORMWATER DRAIN
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m^^m^>>m.
pm^mmm
chor points
150 min,
150 min.
DIMENSIONS IN MILLIMETRES
FIGURE 8.10 ANCHORING OF SITE STORMWATER DRAINS
8.11 ON-SITE STORMWATER DETENTION (OSD) SYSTEMS
8.11.1 General criteria
OSD systems, located both above and below ground, shall comply with the following:
(a) Provision shall be made for the harmless escape of overflows in the event that an
outlet gets blocked and the storage is completely filled. Any ponding of water
resulting from a blockage shall occur at a visible location, so that the fault can be
noticed and corrected.
(b) Ponding and overflow levels shall be not less than 300 mm below any adjacent
habitable floor levels of buildings and not less than 150 mm below non-habitable
floor levels.
8.11.2 Above-ground systems
For OSD systems located above the ground, the following criteria are recommended:
(a) in landscaped areas —
(i) a desirable minimum slope for surfaces draining to an outlet be 1:60, and an
absolute minimum slope be 1:100;
(ii) the desirable maximum depth of ponding under design conditions be 300 mm;
(iii) required storage volumes in landscaping areas be increased by 20% to allow for
vegetation growth, construction inaccuracies and possible filling;
(iv) subsoil drains be provided around outlets to prevent the ground becoming
saturated during prolonged wet weather; and
(v) where the storage is located in areas where frequent ponding could cause
maintenance problems or inconvenience, the first 10% to 20% of the storage
required be in an area which can tolerate frequent inundation, such as a paved
outdoor entertainment area, a small underground tank, a permanent water
feature, or a rockery.
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(b) In driveway and car park storages —
(i) depths of ponding to not exceed 200 mm under design conditions;
(ii) transverse paving slopes within storages be not less than 1 : 140; and
(iii) where the storage is located in commonly used areas where ponding would
cause inconvenience, part the storage required be provided in an area or form
which will not cause a nuisance.
NOTE: The appropriate proportion of the storage will depend on the local rainfall climate, but
15% would be an indicative value. As a further guide, ponding outside this area should only occur
approximately once every year, on average.
8.11.3 Below ground systems
OSD systems located in underground tanks shall comply with the following:
(a) The hydraulic control for the storage, usually an orifice plate on an outlet pipe, shall
be firmly fixed in place to prevent removal or tampering. (A suitable plate may be of
3 to 5 mm thick stainless steel with a circular hole of the diameter required by the
designer machined to 0.5 mm accuracy. The machined hole is to retain a sharp edge.)
The orifice diameter shall be not less than 25 mm.
(b) For tanks with open storage zones, allowance shall be made for the accumulation of
debris and sediment in the storage, as follows:
(i) Floors of tanks shall be graded at a minimum slope of 1:140 towards the outlet,
to minimize ponding and depositing of debris.
(ii) An inspection/access opening shall be provided above the location of the outlet
with dimensions at least 600 mm x 600 mm or 600 mm diameter for storages up
to 800 mm deep and 600 mm x 900 mm for deeper storages. There shall be no
impediments to the removal of debris through this opening. Inspection shall be
possible without residents or owners having to remove heavy access covers.
(iii) When storages are not sufficiently deep to work in (i.e., less than 1.5 m deep),
access shall be provided at intervals of approximately 10 m to allow the system
to be flushed to the storage outlet. Adequate access shall be provided at the
outlet.
(iv) A sump (with a base level set below that of the main storage) shall be provided
at the outlet point, set below the level of the main storage to collect debris.
Where a discharge control pit is included in the storage, this shall contain a
sump set a minimum of 1 .5 times the diameter of the orifice of the outlet below
the centre of the orifice. Sumps shall be provided with adequate weepholes to
drain out to the surrounding soil, and shall be founded on a compacted granular
base.
(c) Where the depth of the tank exceeds 1.2 m, a ladder in accordance with
Clause 8.6.6.2 shall be installed.
(d) Below ground OSD systems shall comply with AS/NZS 2865.
It is recommended that underground tanks comply with the following:
(A) Screens with the following characteristics be provided to cover each orifice outlet:
(1) For orifices up to 150 mm diameter, a fine aperture-expanded metal mesh
screen (BHP Maximesh Rh3030 or equivalent) with a minimum area of
50 times the area of the orifice. For larger diameter orifices, a coarser grid mesh
with a minimum area of 20 times the orifice area may be used as an alternative.
(2) Steel screens be of stainless steel or hot-dipped galvanized.
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(3) Where aperture-expanded mesh screens are employed, they be positioned so
that the oval-shaped holes are horizontal, with the protruding lip angled
upwards and facing downstream. A handle may be fitted to ensure correct
orientation and easy removal for maintenance.
(4) Screens be located so that they are at least 1.5 times the orifice diameter or
200 mm from the orifice plate, whichever is the greater.
(5) Screens be placed no flatter than 45° to the horizontal in shallow storages up to
600 mm deep. In deeper or more remote locations, the minimum angle should
be 60° to the horizontal.
(B) If the storage is sealed, a vent be provided to expel any noxious gases.
(C) The storage be designed to fill without causing overflows in upstream conduits due to
backwater effects.
NOTE: A system may provide a cellular storage volume rather than an open void, and some may
permit infiltration to the surrounding soil.
8.11.4 Materials
Storages shall be constructed of concrete, masonry, aluminium/zinc alloy-coated steel, zinc-
coated steel, galvanized iron or plastics.
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SECTION 9 PUMPED SYSTEMS
9.1 SCOPE OF SECTION
This Section specifies criteria for pumped systems.
9.2 GENERAL
Pumped systems are for areas normally less than 2000 m^ where it is not possible for the
stormwater to be discharged by gravity through the available gravitational point of
connection.
The pumping equipment shall include a wet well, pumps and motors, pipework and
electrical equipment and be located to facilitate easy connection to either the surface water
system or the pumped point of connection,
NOTE: An illustration of the application of this Section is given in Appendix L.
9.3 WET WELLS
9.3.1 General
Wet wells, for submersible or non-submersible type pumps, shall be installed in accessible
locations.
9.3.2 Construction and materials
The structure shall be sound and constructed of materials that will resist corrosion from
ground water and aggressive soils.
Authorized materials include pre-cast or cast in situ reinforced concrete, corrosion-resistant
metals, brickwork or glass-reinforced plastics.
9.3.3 Base
The base shall be constructed of materials compatible with the walls and shall maintain a
self-cleansing gradient towards the pump inlet. The base shall be supported on stable
ground.
9.3.4 Cover
The cover shall be constructed of similar materials to that of the wet well and sball have
removable access openings sized for maintenance purposes. If the access opening is
airtight, a breather pipe with a non-corrodible screen shall be installed.
9.3.5 Ladders
Where a wet well exceeds a depth of 1.2 m, a ladder, in accordance with Clause 8.6.5.4,
shall be installed.
9.3.6 Combined effective storage
The capacity of the pumped system shall be achieved by a combination of pump capacity
and wet well storage between the high and low working levels of the wet well. The
combined effective storage comprising the volume able to be pumped in 30 min plus the
wet well storage shall not be less than the volume of the run-off from the storm of
AR] ^ 10 years and duration of 120 min, or as otherwise directed by the authority having
jurisdiction. The maximum pump capacity shall be as detailed in Clause 9.4(a). The
minimum wet well storage between the high and low working levels expressed in cubic
metres shall be 1% of the catchment area in m^ but in any case shall not be less than 3 m\
NOTE: The minimum pump capacity should be 10 L/s.
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95 AS/N/S 3500.3:2003
9.3.7 Alarm
High-level and low-level alarms shall be installed in each wet well and located clear of the
discharge from the inlet pipe so that false alarms are prevented. The high level alarm should
be set no higher than 100 mm above the invert of the inlet pipe, provided that flooding of
habitable or storage areas and vehicle garages shall be avoided. Where Hooding could occur
the overflow and high-level alarm shall be lowered accordingly to prevent flooding.
9.3.8 Inlet
The invert of the inlet pipe to the wet well shall be located at least 100 mm above the level
of the Design Top Water Level.
9.3.9 Sealing
All pipes or apparatus passing through a wall or cover of a wet well shall be sealed with a
compatible material.
9.4 PUMPS
The pumps shall be suitable for unscreened stormwater and shall be installed as follows;
(a) Pumps shall be in duplicate. The maximum capacity of each pump shall be selected so
that the capacity of the system receiving the discharge is not exceeded. The pump
controls shall be set up to enable alternate pump operation at each start. In the event
that a pump fails to operate when the water level in the wet well reaches the pump
start, the other pump shall be activated and a visible alarm initiated. In the event that
both pumps fail to operate, an audible alarm shall be initiated,
(b) Pumping equipment shall be securely fixed to the wet well using corrosion-resistant
fixings.
(c) Pumps shall be fitted with a gate valve and non-return valve on the delivery side of
each pump.
(d) Pumps shall have flanges or unions installed to facilitate removal.
(e) Pumps shall be controlled so as to limit the number of starts per hour to within the
capacity of the electrical motors and equipment, and shall, as far as practicable,
empty the contents of the wet well at each operation.
(f) The required pumping rate shall be calculated based on an assessment of the expected
inflow and, where appropriate, the allowable discharge rate,
9.5 RISING MAINS
Rising mains shall comply with the relevant Sections of AS/T^JZS 3500.1 and this Standard,
and connect to —
(a) a stormwater or inlet pit; or
(b) direct to a stormwater drain.
9.6 ELECTRICAL CONNECTION
All electrical motors and equipment shall be installed in accordance with AS/NZS 3000.
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96
SECTION 10
S I T E TESTING
10.1 SCOPE OF SECTION
This Section specifies criteria for the testing of downpipes within buildings, site stormwater
drains and main internal drains under buildings and all rising mains.
10.2 DOWNPIPES, SITE STORMWATER DRAINS AND DRAINS WITHIN OR
UNDER BUILDINGS
Downpipes, site stormwater drains and drains within or under buildings shall be tested in
accordance with Clause 10.3
10.3 TEST CRITERIA
10.3.1 Downpipes within buildings
Downpipes within buildings shall be free of leaks when subject to either —
(a) water test at a pressure of a head of water equal to the lesser of 10 m or the length of
the downpipe for a period of not less than 10 min; or
(b) air test at a pressure of not less than 30 kPa for a period of not less than 3 min.
Note: I kPa = 100 mm head of water.
10.3.2 Site stormwater drains, drains within and under buildings and main-internal
drains
Site stormwater drains, drains within and under buildings and main internal drains shall be
free of leaks when subjected to either of the following:
(a) Water test (see Clause 10.4.1) The leakage rate not to exceed the relevant value
given in Table 10.1 for a pressure within the range 1.5 m to 3.0 m head of water
maintained for a period of not less than—
(i) 10 min for FRC, precast concrete (steel reinforced) and vitrified clay (ceramic)
products; or
(ii) 5 min for all other authorized products,
(b) Air test (see Clause 10.4.2) Application of a pressure test of not less than 30 kPa for
a period of not less than 3 min then, after disconnection of the pressure source, the
period for a pressure drop from 25 kPa to 20 kPa to exceed the relevant value given in
Table 10.2,
TABLE 10.1
MAXIMUM LEAKAGE RATE
Material
IMaximum leakage rate per 30 m length
L/min
FRC, precast concrete (steel reinforced) and
viLrilled clay (ceramic)
DN
1000
All other authorized
Nil
10.3.3 Rising mains
Rising mains shall be free of leaks when subject to a pressure test at a pressure of not less
than twice the shut-off head of the pump connected to the rising main, fbr a period of not
less than 10 min.
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AS/NZS 3500.3:2003
TABLE 10.2
MlNrMUM PERIOD FOR PRESSURE DROP
Nominal size
DN
Minimum period for
pressure drop from 25 kPa
to 20 kPa
s
100 to 225
300 to 450
90
180
10.4 PROCEDURE
10.4.1 Water test
The head of water on any section of drain shall not exceed 3 m.
The procedure shall be as follows:
(a) Seal all openings except the top of the section of the below-ground drain to be tested.
(b) Fill the below-ground drain with water to the highest level in that section.
(c) Maintain the water at this level for a period of —
(i) 10 min for vitrified clay drains, by the addition of measured quantities of make-
up water as set out in Item (c); or
(ii) 5 min for drains of any other material.
The test is considered to be successful if no make-up water is required.
TslOTE: For vitrified clay drains the following quantities of make up water are permitted —
(a) up to 1 L per 30 m length of DT^ 100; or
(b) up to 1 .5 L per 30 m length of DT^ 1 50.
10.4.2 Air test
The procedure shall be as follows:
(a) Apply a pressure of 30 kPa to the drain and hold this pressure for 3 min to allow the
air temperature to stabilize.
(b) Shut off the air supply and measure the time taken for the pressure in the pipe to drop
from 25 kPa to 20 kPa.
The drain is considered to have passed the test if the time taken is greater than 90 s for
pipes of size DN 225 or smaller, or 1 80 s for pipes of sizes DN 300 and DN 375.
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APPENDIX A
REFERENCED AND RELATED DOCUMENTS
(Normative)
Al REFERENCED DOCUMENTS
The following documents are referred to in this Standard:
AS
1074 Steel tubes and tubulars for ordinary service
I 100 Technical drawing
1 100.101 Part 101 : General principles
1 1 67 Welding and brazing — Filler metals
1 167.1 Filler metal for brazing and braze welding
1 273 Unplasticized PVC (UPVC) downpipe and fittings for rainwater
1289 Methods of testing soils for engineering purposes
1289.5.4,1 Method 5.4.1 : Soil compaction and density tests — Compaction control test —
Dry density ratio, moisture variation and moisture ratio
1289.5.6.1 Part 5.6.1: Soil compaction and density tests — Compaction control test —
Density index method for a cohesionless material
1 345 Identification of the contents of pipes, conduits and ducts
1379 Specification and supply of concrete
1432 Copper tubes for plumbing, gasfitting and drainage applications
1478 Chemical admixtures for concrete, mortar and grout
1478.1 Part 1 : Admixtures for concrete
1 604 Specification for preservative treatment
1 604.1 Part 1 : Sawn and round timber
1628 Water supply — Metallic gate globe and non-return valves
1 631 Cast grey and ductile iron non-pressure pipes and fittings
1657 Fixed platforms, walkways, stairways and ladders — Design, construction and
installation
1665 Welding of aluminium structures
1761 Helical lock-seam corrugated steel pipes
1762 Helical lock-seam corrugated steel pipes — Design and installation
1834 Material for soldering
1834.1 Part 1: Solder alloys
2032 Code of practice for installations of UPVC pipe systems
2033 Installation of polyethylene pipe systems
2050 installation of roof tiles
2200 Design charts for water supply and sewerage
2439 Perforated plastics drainage and effluent pipe and fittings
2439.1 Part 1 : Perforated drainage pipe and associated fittings
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2638 Gate valves for waterworks purposes
2638.1 Part 1: Metal seated
2638.2 Part 2: Resilient seated
AS
2758 Aggregates and rock for engineering purposes
2758.1 Part 1: Concrete aggregates
3517 Capillary fittings of copper and copper alloy for non-pressure sanitary
plumbing applications
3571 Glass filament reinforced thermosetting plastics (GRP) pipes — Polyester based
— Water supply, sewage and drainage applications
3578 Cast iron non-return valves for general purposes
3600 Concrete structures
3648 Specification and methods of test for packaged concrete mixes
3673 Malleable cast iron threaded pipe fittings
3680 Polyethylene sleeving for ductile iron pipelines
3705 Geotextiles — Identification, marking and general data
3725 Loads on buried concrete pipes
3795 Copper alloy tubes for plumbing and drainage applications
3996 Metal access covers, road grates and frames
4058 Precast concrete pipes (pressure and non-pressure)
4060 Loads on buried vitrified clay pipes
4087 Metallic flanges for waterworks purposes
4139 Fibre-reinforced concrete pipes and fittings
4198 Precast concrete access chambers for sewerage applications
AS/NZS
1 1 67 Welding and brazing — Filler metals
1 1 67.2 Filler metal for welding
1254 PVC pipes and fittings for storm and surface water applications
1260 PVC pipes and fittings for drain, waste and vent applications
1477 PVC pipes and fittings for pressure applications
1 170 Structural design actions — General principles
ri70.1 Part 1: Structural design actions — Permanent, imposed and other actions
1 170.3 Part 3: Structural design actions — Snow and ice actions
1866 Aluminium and aluminium alloys — Extruded rod, bar, solid and hollow shapes
2 1 79 Specifications for rainwater goods, accessories and fasteners
2179.1 Parti: Metal shape or sheet rainwater goods, and metal accessories and
fasteners
2179.2(Int) Part 2: PVC rainwater goods and accessories
2280 Ductile iron pressure pipes and fittings
2312 Guide to the protection of iron and steel against exterior atmospheric corrosion
by the user of protective coatings
2566 Buried flexible pipelines
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AS/NZS 3500.3:2003 100
2566,1 Part 1: Structural design
2865 Safe working in a confined space
2878 Timber— Classification into strength groups
3000 Electrical installations
3500 Plumbing and drainage
3500.0 Part 0: Glossary of terms
AS/NZS
3500.1 Part 1 : Water services
3879 Solvent cements and priming fluids for use with unplasticized PVC (uPVC)
pipes and fittings
4020 Testing of products for use in contact with drinking water
4129 Fittings for polyethylene (PE) pipes for pressure applications
4130 Polyethylene (PE) pipes for pressure applications
4327 Metal-banded flexible couplings for low-pressure applications
4401(lnt) High-density polyethylene (PE-HD) pipes and fittings for soil and waste
discharge (low and high temperature) systems inside buildings — Specifications
4455 Masonry units and segmental pavers
4671 Steel reinforcing materials
4680 Hot-dip galvanized (zinc) coatings on fabricated ferrous articles
NZS
3107 Specification for precast concrete drainage and pressure pipes
3631 New Zealand timber grading rules
3640 Specification of the minimum requirements of the NZ Timber Preservation
Council Inc.
5807 Code of Practice for industrial identification by colour, wording or other
coding
BS
EN 295-1 Vitrified clay pipes and fittings and pipe joints for drains and sewers.
Requirements.
EN 12056- Gravity drainage systems inside buildings. Roof drainage, layout and
3 calculation
6367 Code of practice for drainage of roofs and paved areas
8301 Code of practice for building drainage
ASTM
A240 Standard Specification for Chromium and Chromium-Nickel Stainless Steel
Plate, Sheet, and Strip for Pressure Vessels and for General Applications
E1/AS1 NZ Building Code Approved Documents: Acceptable solutions E1/AS1
ARR87 Australian rainfall and runoff: A guide to flood estimation. Volumes 1 and 2.
Revised edition 1998, published by Institution of Engineers Australia
BCA Building Code of Australia: Volume 1 — Class 1 and Class 10 Buildings —
Housing Provisions; Volume 2 — Class 2 to Class 9 Buildings, Australian
Building Codes Board
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101 AS/NZS 3500.3:2003
PCA Plumbing Code of Australia
A2 RELATED DOCUMENTS
Attention is drawn to the following related documents:
1 Beecham S.C., Jones R.F., O'Loughlin G.G. (1995), Hydraulic testing of box and
valley gutters for roof drainage design, Second International Symposium on Urban
Stormwater Management, Institution of Engineers, Australia.
2 Argue, J.R. (1986), Storm drainage design in small urban catchments: a handbook for
Australian practice. Special Report No. 34, Australian Road Research Board,
Vermont South.
3 Meville Jones & Associates Pty Ltd and Australian Water Engineering (1992),
Queensland Urban Drainage Manual, 2 volumes, Queensland Water Resources
Commission, the Local Government Engineers' Association of Queensland and
Brisbane, City Council, Brisbane.
4 ACT Department of Urban Services (1994), Urban Stormwater, Edition 1, Standard
Engineering Practices, Australian Government Publishing Service, Canberra.
5 Upper Parraniatta River Catchment Trust (1999) On-site Stormwater Detention
Handbook, 3rd Edition, Parramatta (available from www.uprct.nsw.gov.au).
6 Sydney Coastal Councils Group, On-Site Stormwater Detention Guidelines for Urban
Councils (draft), Sydney, 1995.
7 Martin K. G. and Tilley R.I, 1968. Influence of slope upon discharge capacities of
roof drainage channels CSIRO Aust, Division of Building Research. Rpt. 0.2.2-32.
8 REBUILD, December 1976, published by CSIRO, Division of Building Research.
9 New Zealand Building Code, published in New Zealand. Building Industry Authority.
10 General drainage manuals prepared by other authorities, and manuals prepared by
municipal councils for local use.
11 Ralph Jones & Eugene Kloti (1999) A High Capacity Overflow Device for Internal
Box Gutters of Roofs. 8th International Conference on Urban Storm Drainage 30.8.99
to 3.9.99, Institution of Engineers, Australia.
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102
APPENDIX B
SITE-MIXED CONCRETE FOR MINOR WORKS
(Informative)
Minor works are deemed to be works of a minor nature in which the strength of the concrete
is not critical. For such works it is permissible for the designer to specify the proportions
given in Table Bl . Strength tests are not required for minor works.
It is permissible to adjust the proportions of fine and coarse aggregates given in Table Bl
so long as the ratio there stated of total aggregate to cement is not changed.
TABLE Bl
CONCRETE MIX PROPORTIONS FOR MINOR WORKS
(The proportions listed in this Table do not apply to lightweight concrete and concrete
made with blended cement)
1
2
3
4
5
6
Mix proportions by mass for saturated surface-
dry dense aggregate
Maximum
slump
Maximum
water/cement
ratio by mass
Nominal
strength
Cement
Fine
aggregate
Coarse
aggregate
mm
MPa
1
2/2
4
100
0.70
15
1
2
3
100
0.58
20
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APPENDIX C
STORMWATER DRAINAGE INSTALLATION PLANS
(Informative)
CI SCOPE
This Appendix sets out guidelines for the use of network utility operators, to indicate the
information that may be included in stormwater drainage installation plans.
Where requested these plans may comprise —
(a) a roof plan for all building to be fitted with rainwater goods;
(b) a site plan;
(c) where applicable, a catchment plan; and
(c) computation sheets for the general method.
C2 ROOF PLAN
C2.1 Building with fewer than four floor levels
Roof plans for buildings with fewer than four floor levels should be drawn to a scale not
smal ler than 1 : 1 00 and show —
(a) extent and slope of roofs for each building and details of any adjacent parapets or
vertical walls; and
(b) proposed layout, sizes and, as applicable, gradients of gutters, downpipes, overllow
devices and surcharge outlets.
C2.2 Buildings with four or more floor levels
Roof plans for buildings with four or more floor levels should comprise —
(a) the information required in Paragraph C2. 1 ; and
(b) an isometric line diagram (see AS 1100.101), or such other three dimensional
representation authorized by the network utility operator, to show the catchment area,
location, size and, if applicable, the gradient of each downpipe.
C3 SITE PLAN
Site plans should be drawn to a scale not smaller than 1:500 and in Australia to the
Australian Height Datum (AHD) or in New Zealand to the datum authorized by the network
utility operator and show —
(a) boundaries and topography of the property, i.e., spot levels or contours to the
appropriate datum;
(b) location of all existing and proposed buildings and the levels of ground and basement
floors, to the appropriate datum;
(c) location(s) and invert level(s) of the point(s) of connection for the property;
(d) proposed layout, sizes, invert levels and gradients of the elements, including overflow
paths for storms of the surface water drainage system.
(e) proposed layout and sizes of elements of the subsoil drainage system; and
(f) vehicular washing areas.
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AS/NZS 3500,3:2003 104
C4 CATCHlVrENT PLAN
Catchment plans should be drawn to a scale not smaller than that authorized by the network
utility operator and show —
(a) boundaries of the property; and
(b) limits and topography of the catchment area(s) draining to the property, to the
appropriate datum.
C5 COMPUTATION SHEETS
Computation sheets under the general method should clearly show the basic assumptions
and the calculations necessary for the sizing of the elements specified in Paragraphs C2 and
C3.
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105 AS/NZS 3500.3:2003
APPENDIX D
GUrDELlNES FOR DETERMINING RAINFALL INTENSITIES
(Informative)
Dl SCOPE
This Appendix sets out guidelines for determining for any place in —
(a) Australia, rainfall intensities for 5 min duration and ARls of 20 and 100 years; and
(b) New Zealand, rainfall intensities for 10 min duration and ARIs of 10 and 50 years.
NOTE: Significant inaccuracies can occur for any ARI that exceeds the available period of
rainfall records. The expected probability is discussed in ARR87.
D2 PROCEDURES
02.1 Australia
The procedure for the determination of rainfall intensities, in millimetres per hour, for the
place considered is as follows:
(a) If given in Table El and —
(i) shown in Figures E2 to El 3, either —
(A) read directly from the relevant Figure; or
(B) submit the latitude and longitude (see Table El) with a request for the
required rainfall intensities to the Hydrometeorological Advisory
Services of the Bureau of Meteorology (HASBM)*; or
(ii) not shown in Figures E2 to El 3, either —
(A) plot its position (see Table El) on the relevant Figure and read directly
from the Figure; or
(B) repeat Step (a)(i)(B),
(b) If not given in Table El, determine the latitude and longitude from a map of an
appropriate scale and either —
(i) plot its position on and read directly from the relevant Figure; or
(ii) submit the latitude and longitude with a request for the required rainfall
intensities to the HASBM*.
D2.2 New Zealand
The procedures for the determination of rainfall intensities, in millimetres per hour, for the
place considered is as follows:
(a) If shown in Figures Fl to F4, read directly from the relevant Figure (see
Paragraph F2).
(b) If not shown in Figures Fl to F4, determine the latitude and longitude from a map of
an appropriate scale and either —
(i) plot its position on and read directly from the relevant Figure; or
(ii) submit the latitude and longitude with a request for the required rainfall
intensity to the National Institute for Water and Atmosphere (NIWA).
* Although a service fee is charged, this is the preferred option for applications that require a high degree oi"
accuracy or for places where there is a significant gradient between the isopleths (lines of equal rainFall
intensity) on the relevant Figure, or both.
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AS/N/.S 3500.3:2003 106
APPENDIX E
RAINFALL INTENSITIES FOR AUSTRALIA— 5 MIN DURATION
(Normative)
El SCOPE
This Appendix gives 5 min duration rainfall intensities, for any place in Australia, that are
based on the Computerized Design Intensity — frequency — duration Rainfall System
(CDIRS) data of the Bureau of Meteorology, used for the sizing of —
(a) rainwater goods (see Clause 3.3.5.1); and
(b) surface water drainage systems (see Clause 5. 4, 5(a)).
E2 SELECTED PLACE REFERENCES
For selected places in Australia, the area number (see Figure El), the latitude and longitude
and the reference figure (Figures E2 to El 3) are given in Table El.
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AS/NZS 3500.3:2003
TABLE El
SELECTED PLACE REFERENCES
Area
number
Latitude
south
Longitude
east
Reference figure
Place
ARI, years
20
100
Abydos
6
21.47°
118.92°
El 2
1 :: 1 3
Adelaide (CBD)
3
34.93°
138.60°
B6
E7
Albany
6
35.03°
117.88°
El 2
E13
Albury
3
36.08°
146.91°
i;:6
E7
Aliee Springs
3
23.70°
133.88°
E6
E7
Arkaroola
3
30.32"
139.33°
E6
E7
Armidale
1
30.50°
151.67°
B2
E3
Bacchus Marsh
3
37.68°
144.44°
E6
E7
Ballarat
3
37.56°
143.86°
E6
E7
Bale mans Bay
2
35.71°
150.18°
E4
125
Balhursl
2
33.42°
149.56°
E4
E5
Benalla
3
36.55°
145.98°
E6
E7
Biloela
5
24.40°
150.51°
ElO
Ell
Bowral
2
34.48°
150.42°
E4
E5
Bridgewater
4
42.74°
147.24°
E8
E9
Brisbane (CBD)
1
27.47°
153.03°
E2
E3
Broken Hill
3
31.93°
141.47°
E6
E7
Broonne
6
17.96°
122.24°
El 2
E13
Bun bury
6
33.33°
115.64°
El 2
El 3
Bundaberg
5
24.87°
152.35°
ElO
E 1 1
Burnie
4
41.05°
145.91°
E8
E9
Cairns
5
16.93°
145.78°
ElO
Ell
Canberra (CBD)
2
35.28°
149.12°
1Z4
E5
Cape York
3
11.45°
142.43°
E6
E7
Carnarvon
6
24.89°
113.66°
El 2
E13
Casino
1
28.87°
153.05°
B2
E3
Ceduna
3
32.13°
133.68°
EG
E7
Charleville
3
26.4 r
146.24°
Ed
E7
Charters Towers
5
20.08°
146.26°
ElO
Ell
Cloncurry
3
20.71°
140.51°
E6
E7
ColTs Harbour
1
30.30°
153.12°
E2
E3
Collie
6
33.36°
116.16°
El 2
EL3
Cooma
2
36.23°
149.11°
E4
E5
Coonabarabran
1
31.28°
149.27°
E2
E3
Cowra
3
33.84°
148.69°
E6
E7
Darnpier
6
20.66°
116.71°
El 2
E13
Darwin
3
12.46°
130.84°
E6
E7
Deloraine
4
41.53°
146.65°
B8
E9
Derby
6
17.31°
123.63°
El 2
E13
Dorrigo
1
30.34°
152.71°
E2
E3
Dover
4
43.31°
147.01°
i;':8
E9
Dubbo
3
32.35°
148.61°
E6
E7
(contiyiued)
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AS/NZS 3500.3:2003
108
TABLE El {continued)
Area
number
Latitude
south
Longitude
east
Reference figure
Place
ARI, years
20
100
Emerald
5
23.52°
148.16°
E10
Ell
ninders island
4
40.03°
148.05°
E8
E9
Forbes
3
33.38°
148.00°
E6
E7
Gee long
3
38.15°
144.36°
E6
E7
Gerald ton
6
28.78°
114.61°
E12
El 3
Glen Innes
1
29.74°
151.74°
E2
E3
Goondiwindi
1
28.55°
150.30°
E2
E3
Gosford
2
33.43°
151.34°
E4
E5
Go ul burn
2
34.76°
149.72°
E4
E5
Gympie
1
26.19°
152.66°
i:^2
E3
Halls Creek
6
18.23°
127.66°
El 2
EE3
liamersley
6
31.85°
115.79°
E12
El 3
Hamilton
3
37,75°
142.01°
E6
E7
Healesville
3
37.65°
145.52°
E6
El
Hillside
2
33.58°
150.97°
E4
E5
1 lobart (CBD)
4
42.88°
147.33°
E8
E9
Horsham
3
36.71°
142.20°
i;:6
E7
Hughenden
5
20.84°
144.20°
ElO
Ell
Innisfail
5
17.52°
146.03°
EiO
Ell
Inverell
1
29.78°
151.11°
E2
E3
Kalgoorlie
6
30.75°
121.47°
El 2
El 3
Katanning
6
33.68°
117.55°
El 2
El 3
Rather in e
3
14.46°
132.30°
E6
1:^:7
Kempsev
1
31.08°
152.84°
E2
E3
Kiama
2
34.67°
150.85°
E4
E5
Kiandra
3
35.48°
148.87°
E6
E7
Kingaroy
1
26.55°
151.84°
E2
E3
Kingston
4
42.98°
147.31°
E8
E9
Korumburra
3
38.43°
145.82°
E6
E7
Kununurra
6
15.77°
128.74°
El 2
E13
Lakes Entranee
3
37.88°
147.99°
E6
E7
Eauneeston
4
41.44°
147.14°
E8
E9
Eismore
1
28.81°
153.28°
E2
E3
Eithgow
2
33.48°
150.13°
E4
E5
Eongreach
5
23.45°
144.25°
EIO
EEl
Maekay
5
21.15°
149.19°
EIO
El I
Maitland
1
32.74°
151.56°
E2
E3
Marble Bar
6
21.17°
119.74°
E12
El 3
Mareeba
5
16.99°
145.42°
EIO
EEl
Meekatharra
6
26.60°
118.50°
E12
El 3
Melbourne (CBD)
3
37.82°
144.96°
E6
E7
Merimbula
2
36.89°
149.91°
E4
E5
Mildura
3
34.19°
142.16°
E6
E7
Mittagong
2
34.45°
150.45°
EA
E5
(continued)
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AS/NZS 3500.3:2003
TABLE El {continued)
Area
number
Latitude
south
Longitude
east
Reference figure
Place
ARI, years
I 1 \M B 1 I WkM X^ I
20
100
Morwell
3
38.24°
146.40°
E6
E7
Mt Barker
3
35.07°
138.86°
E6
E7
Ml Gam bier
3
37.83°
140.78°
E6
E7
Mt Isa
3
20.73°
139.49°
B6
i;i:7
M(; Morgan
5
23.65°
150.39°
BIO
Ell
Ml Wellington
4
147.23°
42.90°
IZ8
i;'.9
Mullumbimby
1
28.56°
153.50°
E2
E3
Mundaring
6
31.90°
116.16°
El 2
El 3
Murray Bridge
3
35.12°
139.27°
E6
E7
Murwillumbah
1
28.33°
153.39°
E2
E3
Muswellbrook
1
32.27°
150.89°
E2
E3
Newcastle
1
32.93°
151.78°
B2
E3
Mewman
6
23.36°
119.73°
El 2
E13
New Norfolk
4
42.78°
147.06°
E8
E9
Noosa
1
26.41°
153.09°
1:2
E3
Nowra
2
34.88°
150.60°
E4
E5
Muriootpa
3
34.48°
138.99°
E6
i?:7
Orange
2
33.29°
149.10°
B4
E5
Orbosl
3
37.71°
148.46°
E6
E7
Perth (CBD)
6
31.95°
115.86°
El 2
El 3
Port Augusta
3
32.49°
137.76°
E6
i:':7
Port Hedland
6
20.31°
118.57°
El 2
EI3
Port Maequarie
1
31.43°
152.91°
E2
E3
Port Pirie
3
33.18°
138.00°
E6
E7
Proserpine
5
20.40°
148.58°
ElO
Ell
Queenstown
4
42.08°
145.57°
E8
E9
Robertson
2
34.59°
150.59°
E4
E5
F'loekhampton
5
23.38°
150.51°
ElO
El 1
Koma
3
26.57°
148.80°
E6
E7
Roy Hill
6
22.60°
119.95°
E12
El 3
Scotlsdale
4
41.16°
147.52°
E8
1:9
Singleton
1
32.61°
151.17°
E2
E3
Sorell
4
42.79°
147.56°
E8
E9
Soulhporl
1
27.97°
153.41°
E2
1:^3
Stawell
3
37.06°
142.78°
E6
E7
St Helens
4
41.32°
148.24°
E8
E9
Si Marys
4
41.58°
148.18°
i;^:8
E9
Swansea
4
42.12°
148.07°
E8
E9
Sydney (CBD)
2
33.87°
151.21°
1:4
E5
Taree
1
31.91°
152.46°
E2
E3
Tom Priee
6
22.69°
117.79°
EI2
EI3
Toowoomba
1
27.56°
151.96°
E2
E3
Towns vi lie
5
19.26°
146.82°
E 1
Ell
Tweed Heads
1
28.17°
153.54°
i;z2
E3
(coniiniied)
COPYRIGHT
AS/NZS 3500.3:2003
no
TABLE El {continued)
Area
number
Latitude
south
Longitude
east
Reference figure
Place
ARI, years
20
100
Warwick
Weipa
Wittenoom
Wollongt^ng
WonLliaggi
Wyong
Yorketown
1
3
6
2
3
2
3
28.22°
12.63°
22.24°
34.43°
38.61°
33.29^
35.02°
152.03°
141.88°
118.33°
150.89°
145.59°
151.42°
137.60°
E2
E6
B12
E4
E6
E4
E6
E3
E7
El 3
E5
E7
E5
E7
E3 FIVE MINUTES DURATION RAINFALL INTENSITIES
5 mins duration rainfell intensities for ARIs of 20 and 100 years for any place in Australia
may be determined from the following Figures:
(a) Figure El : Location of areas.
(b) Figures E2, E4, E6, E8, ElO and E12: Area numbers 1 to 6, respectively^Rainfall
intensities for an ARI of 20 years.
(c) Figures E3, E5, E7, E9, Ell and E13: Area numbers 1 to 6, respectively — Rainfall
intensities for an ARI of 100 years.
The Figures are marked with isopleths of rainfall intensity (lines of equal rainfall intensity).
COPYRIGHT
Ill
AS/NZS 3500.3:2003
Area 1
Area 4
Prepared by: Hydrometeorological Advisory Service, Melbourne,
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE El LOCATION OF AREAS
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112
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E2 AREA 1— RAINFALL INTENSITIES (mm/h)— 5 MUM— ARI 20 YEARS
COPYRIGHT
1 13
AS/NZS 3500.3:2003
isa
151
15Z
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E3 AREA 1 — RAINFALL INTENSITIES (mm/h)— 5 MIN— ARI 100 YEARS
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114
Prepared from CDIRS by; Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E4 AREA 2 — RAINFALL INTENSITIES (mm/h)— 5 MIN— ARI 20 YEARS
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115
AS/NZS 3500.3:2003
149*
150
152-E
33-S
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E5 AREA2— RAINFALL INTENSITIES (mm/h)— 5 MIN—ARMOO YEARS
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116
129- 130'
146"
149-E
Tiers
Prepared from CDIRS by; Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E6 AREA3— RAINFALL INTENSITIES (mm/h)— 5 MIN—ARI 20 YEARS
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ig gr I3cr
10'
134*
13B*
\4Z
\4^ 140-E
T 1 — ^las
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E7 AREA 3— RAINFALL INTENSITIES (mm/h)— 5 MIN— ARI 100 YEARS
COPYRIGHT
A S/NZS 3500,3:2003
145-
146'
14T
149'E
40" S
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E8 AREA4— RAINFALL INTENSITIES (mm/h)— 5 MIN—ARI 20 YEARS
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AS/NZS 3500.3:2003
144'
145'
146*
14r
148'
ug-E
40' S
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E9 AREA4— RAINFALL INTENSITIES (mm/h)— 5 MIN—ARMOO YEARS
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120
A I
146'
148'
150-
15^
154*E
16*S
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E10 AREAS— RAINFALL INTENSITIES (mm/h)— 5 MIN—ARI 20 YEARS
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AS/^ZS 3500.3:2003
Al
146-
148"
150*
15Z
154*E
iiers
- IB-
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE Ell AREAS— RAINFALL INTENSITIES (mm/h)— 5 MIN— ARI 100 YEARS
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AS/NZS 3500.3:2003
122
128- 129'E
13-3
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E12 AREA6— RAINFALL INTENSITIES (mm/h)— 5 MIN—ARI 20 YEARS
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A S/iSZS 3500.3:2003
128* 129-E
13-5
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E13 AREA6— RAINFALL INTENSITIES (nnnn/h)— 5 MIN—ARI 100 YEARS
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APPENDIX F
RAINFALL INTENSmES FOR NEW ZEALAND— 10 MIN DURATION
(Normative)
Fl SCOPE
This Appendix gives lOmin duration rainfall intensities for any place in New Zealand,
based on the Building Industry Authority data, used for the sizing of —
(a) Rainwater goods (see Clause 3.3.5,2); and
(b) Surfece water drainage systems (see Clause 5. 4, 5(b)),
F2 10 MINUTES DURATION RAINFALL INTENSITIES
Rainfell intensities of 10 min duration for ARIs of 10 and 50 years for any place in
New Zealand may be determined from the following Figures:
(a) Figures Fl and F3 — Rainfall intensities for an ARI of 10 years.
(b) Figures F2 and F4 — Rainfall intensities for an ARI of 50 years.
The figures are marked with isopleths of rainfall intensity (lines of equal rainfall intensity).
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Rainfall Intensities (mm/h)« 10m lOy ARI
Prepared by: National Institute of Water and Atmospheric Research Ltd
FIGURE F1 NORTH ISLAND— RAINFALL INTENSITIES (mm/h)— 10 MIN-
ARI 10 YEARS
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126
Rainfall Intensities (nnnn/h)i 10m 50y ARI
36"$-
ss^s-
Prepared by: National Institute of Water and Atmospheric Research Ltd
FIGURE F2 NORTH ISLAND— RAINFALL INTENSITIES (nnnn/h)— 10 MIN-
ARI 50 YEARS
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Rainfall intensities (mm/h): lOm lOy ARI
Prepared by: National Institute of Water and Atmospheric Research Ltd
FIGURE F3 SOUTH ISLAND— RAINFALL INTENSITIES (mm/h)— 10 MIN-
ARI 10 YEARS
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128
Rainfall intensities (nnnn/h): lOnn 50y ARI
Prepared by: National Institute of Water and Atmospheric Research Ltd
FIGURE F4 SOUTH ISLAND— RAINFALL INTENSITIES (mm/h)— 10 MIN-
ARI 50 YEARS
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129 AS/N/S 3500.3:2003
APPENDIX G
EXAMPLES OF OVERFLOW MEASURES FOR EAVES GUTTERS
(Informative)
Gl SCOPE
This Appendix sets out examples of overflow measures for eaves gutters (see Clause 3.5).
G2 FULL LENGTH (CONTINUOUS) OVERFLOWS
Examples of acceptable full-length (continuous) overflows are as follows:
(a) The front bead not less than the dimension h\ below the top of the facia board as
shown in Figure Gl(a) — (weir flow over front of gutter).
(b) The front bead not less than the dimension h[ below the top edge of the back of the
gutter — (weir flow over front of gutter).
(c) Flashing as shown in Figure Gl(b) with the top edge of the flashing not less than h\
above the bead — (weir flow over front of gutter).
(d) Combinations of items (a), (b) or (c).
(e) The top edge of the back of the gutter not less than h^ below the top of the facia board
as shown in Figure Gl(c) — (weir flow over back of gutter).
(f) For concealed eaves gutters the top edge of the facia not less than h[ below the top of
the back of the gutter, or integral flashing (tail) with the top edge of the flashing not
less than h^ above the top of the facia as shown in Figure G 1(d)— (weir flow over
front of gutter).
The h[ value shall be determined from Tabled where the average flow per metre is
determined from the total flow shown in Figure 3.5 divided by the length of the eaves gutter
served by the catchment.
NOTE: Blockages can and do occur anywhere along an eaves gutter causing overtopping that
would not be affected by an overflow device located at the outlet of an eaves gutter, e.g. rainhead
(see Figure 3.7(a)). The overflow devices given in Paragraph G2 are located along an eaves gutter
so that any overtopping is unlikely to cause monetary loss or property damage including damage
to contents of a building. The ARIs for eaves gutters given in Table 3.1 assume the provision o^
appropriate overflow measures.
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130
G3 SPECIFICALLY LOCATED OVERFLOWS
Examples of specifically located overflows are holes and weirs.
TABLE Gl
minimum: Af VALUES
Gutter slope
Average inflow per metre of gutter
(L/s per m)
0.2
0.4
0.6
0.8
1.0
Level gutter
18
20
22
23
25
Sloping gutter
12
14
16
17
19
Minimum hf (mm)
NOTE: Minimum h^ is based on ' '^/^ for Australia and V/]o lor New Zealand. Table Gl ineludes an
allowance for water surlaee undulations and eonstruction tolerances oj^ 19 mm for level gutters and 13 mm
for sloping gutters. Available research suggests that surface undulations may be limited to tlie range 5 mm
to 8 mm, provided that the discharge JVom metal cladding for all roof slopes is directed downwards by
turning down the outside edge. Figure G2 illustrates the elTect.
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AS/N/S 3500.3:2003
h
\
X
J
?r
V
"Eaves
gutte
J:
^^^-^
-Facia
/\
Flashing
Facia
(a) Eaves gutter with low front
(b) Eaves gutter with high front
and rear flashing
n
^f
——10 min.
■ Facia
Eaves gutter
(c) Eaves gutter with high front
and min. 10 mnn gap to fascia
(d) Concealed eaves gutter with tail
FIGURE G1 EAVES GUTTER OVERFLOW METHODS
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132
Metal cladding with
no down-turn
Metal cladding with
down-turn
\ ^^ Flow pattern
Flow pattern
FIGURE G2 ILLUSTRATION OF FLOW PATTERNS FOR METAL ROOF CLADDING
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133 AS/NZS 3500.3:2003
APPENDIX H
GENERAL METHOD FOR DESIGN OF EAVES GUTTER SYSTEMS-
EXAMPLE
(Informative)
HI SCOPE
This Appendix sets out an example that illustrates the application of the general method for
design of solutions for eaves gutters and associated vertical downpipes (see Clause 3.5).
The calculations are presented in an explanatory form to assist first and occasional users.
The adopted order of accuracy in the examples is consistent with the accuracy of the
assumptions on which they are based.
NOTE: Appendix D gives guidelines for the determination for any place in —
(a) Australia, for rainfall intensities of 5 min duration and ARIs of 20 and 100 years; and
(b) New Zealand, for rainfall intensities of 10 min duration and ARIs of 10 and 50 years.
H2 EXAMPLE
H2.1 Problem
A house as shown in Figure HI is to be constructed at Bathurst in New South Wales (see
Figure E4). Determine the layout and size of the external eaves gutters and associated
vertical downpipes that are to discharge to the surface water drainage system for the
following cases:
Case 1: eaves gutter gradients of 1:500 and steeper.
Case 2: eaves gutter gradients flatter than 1 :500,
To assist the understanding of this example the application of Figures 3.5(A) and E4 is
shown in Figure M2,
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AS/NZS 3500.3:2003
134
15
9
4
12
NOrES;
Dimensions include width o(* eaves gutter.
Pitch orroof24°( 1:2.3).
DIMENSIONS IN METRES
FIGURE H1 HOUSE PLAN
H2.2 Case 1 — Sloping eaves gutter
H2 .2.1 Calculation
The calculation below illustrates the application of the procedure shown in Figure 3.4. Each
step designation (for example (a), (b), (c) and so on) has a corresponding letter in the flow
chart.
CASE 1
(a)
From Tabic 3. 1, select 20 years ARl for Australia and 10 years Af^l for New Zealand
(h)
In Australia the design rainfall intensity for external eaves gutters and associated vertical downpipes
will have a 5 min duration. The value for Bathurst in New South Wales is determined from Table E\
and Figure E4 and is 145 mm/h. The application of Figure E4 for this example is shown in Figure 112.
(c)
By physical observations, measurements or plans of the house, record, as shown on Figure 111-
(i) overall dimensions that include an allowance for the widths of the eaves gutters:
(ii) pitch (slope) of the roof; and
(iii) layout of the ridges and valleys
(d)
Determine for the roof of the house:
(i) from Figure 111, the plan area {A^) is 144 m^; and
(ii) from Equation 3.4.3(2) and pitch of the roof, the catchment area(4t.) is 175 m".
(e)
Select gradients Ibr the eaves gutters;
Select 1 :5()0 and steeper
in
Select eaves gutters from a manufacturer's technical data and note the effective cross-sectional areas
/le is 7300 mnr (square fascia)
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AS/NZS 3500.3:2003
CASE 1
(g) Determine, for the selected size of eaves gutter; using Figure 3.5(A) the maximum size of the
catchment of llie roof per vertical down pipe.
Note: This determination is illustrated in Figure H2
The maximum catchment areaT^^^jp of roof per vertical downpipe is 51 m^
(h) Determine for the selected sizes of eaves gutter (see Step (f)) the minimum number of vertical
downpipes iTom AJA^.^^
175
""^ 3A adopt the next higher whole number, which is 4
5/
(i) Select locations, as shown in Figure FI3, for the minimum of Ibur downpipes
(i) where practical, the sub-cafchments have about the same area; and
(ii) a high point is located at an outlet to a valley gutter.
NOTB: /!(, and A^ for the selected sub-catchments are tabulated in Table 111
(j) For this example the catchment area for each sub-eatchment (/^s-c) is not greater than A^^^,. If the area
of one or more catchment areas is greater than the /i^dp then proceed in accordance with one or more
of the following:
(i) Increase the number of vertical downpipes and repeat Steps (g) to (i).
(ii) Re-position vertical downpipes and repeat Step (i).
(iii) Re-position high points and repeat Step (i).
(iv) Increase the size of the eaves gutter, i.e., larger A^, and repeat Steps (0 to (i).
(k) From Table 3.3 the alternative sizes of the vertical downpipes for the selected gradients (see Step (e))
and sizes (see Step (f)) of eaves gutters are 100 mm diameter or 100 mm x 75 mm.
(I) Select overflow measures in accordance with Clause 3.5 if required. Comply with Paragraph G2(a).
Determine the minimum height of fascia above the gutter overflow (//f) to prevent w^ater entering the
building, as follows:
Determine the maximum ini^low per metre of eaves gutter iTom inspection oFthe plan. The maximum
distance in plan from the eaves gutter to the ridge is 4 m. Hence the maximum catchment area per
metre in plan is 4 x 1 ^-^ 4 m^. The value ixir inllow per metre to be used to not be less than
4 X 145/3600 - 0.16 L/s per m. Select down pipe D from Table H 1 (See note in Table HI).
(i) For downpipe D — -A^^ is 43 m^ (see Table HI).
(ii) Rainfall intensity is 145 mm/h (see Step (b)),
(iii) From Figure 3. 5 A Total How is 2.1 F/s
(iv) Length of gutter is 9 m (see Table HI).
(v) Average flow per metre of gutter = 2.1/9 = 0.23 L/s.
(vi) From Table G1 — (sloping gutter) minimum /?p~ 14 mm.
COPYRIGHT
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136
TABLE HI
SUB-CATCHMENT AREAS FOR DOWNPIPES
Vertical downpipc
Sub-catchment
Case 1
Plan area
m^
Catchment
area (A,.,)
Length of
gutter
m
A
38.0
46
15.5
B
33.5
40
12.5
C
37.5
45
17
D
35.5
43
9
Total
144.0
174
54
NOTE: The sub-catchment for the vertical downpipe at D has the
largest ratio of catchment to gutter length.
COPYRIGHT
137
AS/NZS 3500.3:2003
Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of Meteorology, 1991
FIGURE E4 AREA2 — RAINFALL INTENSITIES (mm/h)— 5 MIN—ARI 20 YEARS
(a) Application of Figure E4
'
.„..
-
-
/
J
1
A
A
f
t
7
T
/
/
7
/
/
/
7
I
7
/
'
90,0'
L
/I
/
7^
/
""
1
1
/
o/
\L
/
/
/
7
/
7
7
7
/'
/
7
'
/\ i
'/\
r
/
/
"e
/
/
1
1
/
/
/
/
\2i
/
no
/
/'
/
7
/
/
/
S 70.0-
/
/
/
i
f
//
I
/
/
7
7
4
^
i
20C
7
/
/
7
7.
7
-
^
y
y
-
-
/
/
1
/
/
/
/
/
'.
/
/
7
/
/
7
/
/
50
Y^
y
1 ^°'°
J
/
/
/
/
/
/
/
/
/
7
y
/
r
y
JOC
X
^
^
o
I
J
/
L
L
/
/
1^
f
/
7
/
'>
7
/
,/
7
y
^
\^
50
^
o
A
1
7
/
f
7
/,
/
/
1^
/
y
y
y
X
y
X
35^
pr
00
r
„.
DC
> 40,0-
'i
\
/
/
/
/
7
i
'y.
/
'7
y
X
y
^
X
y
y
^
-^
^
^
^
^
^
^
y
A
< 30.0-
\
i
i
i
/
i
^
^
^
"^
y
^
X
>
X
^
y
^
-^
>
^.
^
<
^ 20.0-
1
^
g
i
<
^
-^
^
^
DE
SI
IN
R/
MN
-A
.L
INI
Eh
Rl
FY
:i
( ^%) C
)R {^°/io>> ^^^^ (TYPICAL)-!
-
-
"-
-
.„
-
-
"
-■"
-
O
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
EFFECTIVE CROSS-SECTIONAL AREA OF EAVES GUTTER* [A^). 1000 mm^
FOR GRADIENTS OF 1 ; 500 AND STEEPER
TOTAL FLOW IN EAVES GUTTER (L/s)
NOTBS:
1 This graph assumes —
(a) an effective width to depth is a ratio of about 2:1;
(b) a gradient in the direction of flow of 1 :5()() or steeper;
(c) the least favourable positioning of the downpipe and bends within the gutter length;
(d) a cross-section or half round, quad, ogee or square; and
(e) the outlet to a vertical down pipe is located centrally in the sole of the eaves gutter.
2 The required eaves gutter discharge areas do not allow for loss of waterway due to internal brackets.
FIGURE H2 APPLICATION OF FIGURE 3.5(A)
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DP-A
LEGEND:
Vertical downpipe
=
e
High point
=
HP
Down pipe
=
DP
„J I....
eDP-B
#DP-C
10 m
1 1 L... .i,._ I
FIGURE H3 ROOF PLAN— CASE 1
B2.2.2 Solution
Adopt the following:
(a) Roof plan as shown in Figure H3 with eaves gutter gradients for Case 1 of 1:500 and
steeper,
(b) Eaves gutters with an effective cross-sectional area of 7300 mm^ (square fascia).
(c) Vertical downpipes of 100 mm diameter or 100 mm x 75 mm rectangular.
(d) Minimum height of fascia above gutter overflow is 14 mm.
H2.3 Case 2 — Flat eaves gutter
H2 .3 . 1 Calculation
The calculation below illustrates the application of the procedure shown in Figure 3.4. Each
step designation (for example (a), (b), (c) and so on) has a corresponding letter in the flow
chart.
CASE 2
(a)
Itoiti Tabic 3.1, select 20 years ARl for Australia and 10 years ARl for New Zealand
(b)
In Australia the design rainfall intensity for external eaves gutters and associated vertical downpipes
will have a 5 mins duration. The value for Bathurst in New South Wales is determined from Table El
and Figure B4 and is 145 mm/h. The application of FMgure E4 Ibr this example is shown in figure 113.
(c)
By physical observations, measurements or plans of the house, record, as shown on Figure 111-
(i) overall dimensions that include an allowance for the widths of the eaves gutters;
(ii) pitch (slope) of the roof; and
(iii) layout of the ridges and valleys
(d)
Determine Ibr the roof of the house:
(i) from Figure HI, the plan area {A\^ is 144 m^; and
(ii) from Equation 3.4.3(2) and pitch of the roof, the catchment area (//^;) is 175 m^
(e)
Select gradients for the eaves gutters; Select Hatter than 1 :500.
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CASE 2
(0
Select eaves gutters from a manufacturers technical data and note the efi^eetive cross-sectional areas
(/IJ; /Ic is 7300 mm" (square fascia)
(g)
Determine, for the selected size of eaves gutter; using Figure 3.5(B), the maximum size of the
catchment of the roof per vertical downpipe.
Note: This determination is illustrated in Figure 114.
The maximum catchment area/tcdp of roof per vertical downpipe is 36 m^
(h)
Determine for the selected sizes of eaves gutter (see Step (f)) the minimum number of vertical
downpipes from AJA^^^
175
= 4.9 adopt the next higher whole number, which is 5.
36
(1)
Select locations, as shown in Figure H5, for the minimum of five downpipes.
The layout in H4 requires precise positioning of the downpipes. in practice it is unlikely that this
could be achieved because of windows, doors, and other features but nevertheless it demonstrates
what happens if the same size eaves gutters arc used for both Cases 1 and 2. With less precise
positioning of the 5 downpipes, a larger eaves gutter would be required
As there are no high points for fiat caves gutters to define the catchment areas for each downpipe and
eaves gutter section, halve the total catchment area between adjacent downpipes to effectively create
imaginary high points somewhere between the selected downpipes.
1 lence, if there are three downpipes in sequence numbered DP-1, DP-2 & Dr^-3, the catchment area of
DP-2 is half the catchment area between DP- 1 and DP-3, irrespective of the position of DP-2.
/fii and Ac, lx)rthe selected sub-catchments are tabulated in Table 112.
(J)
For this example the catchment area for each sub-catchment (//s-c) is not greater than A^dp- If the area
of one or more catchment areas is greater than the A^p then increase the number of vertical downpipes
and repeat Steps (g) to (i).
(k)
From Table 3.3 the alternative sizes of the vertical downpipes for the selected gradients (see Step (c))
and sizes (see Step (1]) of eaves gutters are 85 mm diameter or 100 mm x 50 tnm.
(1)
Select overfiow measures in accordance with Clause 3.5 if required. Comply with Paragraph G2(a).
Determine the minimum height of fascia above the gutter overfiow (/?() to prevent water entering the
building, as follows:
Determine the maximum inflow per metre of eaves gutter from inspection of the plan. The maximum
distance in plan from the eaves gutter to the ridge is 4 m. Hence the maximum catchment area per
metre in plan is 4 x 1 -= 4 m^. The value for infiow per metre to be used shall not be less than
4 X 145/3600 = 0.16 L/s per m. Select downpipe E from Table 112 (See note in Table M2)
(i) For downpipe E — A^^ is 36 m^ (see Table FI2).
(ii) Rainfall intensity is 145 mm/h (see Step (b)).
(iii) From Figure 3.5B Total flow is 1 .7 L/s
(iv) Length of gutter is 9.5 m (see Table H2).
(v) Average fiow per metre of gutter = 1.7/9.5= 0.18 L/s
(vi) From Table Gl — (level gutter) minimum hf^ 18 mm.
The minimum //^ values may not provide sufficient protection where valley gutters discharge to eaves
gutters with zero slope. In such cases, it is recommended that h^- be increased in the vicinity of the
valley gutters. The reason for this is that the valley gutter discharges into an eaves gutter that may
already contain water.
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TABLE H2
SUB-CATCHMENT AREAS FOR DOWNPIPES
Vertical
downpipe
Suh-catchnient
Case 2
Plan area
(Ah, J
Catchment
area (A,.,)
Length of
Gutter*
m
A
29.5
36
11.5
B
29
35
10
C
26.8
32
13
D
29.2
35
10
E
29.5
36
9.5
Total
144
174
54
* Based on half the length between downpipes.
NOTE: The sub-eatchment Ibr the vertical downpipe at
has the largest for ratio of eatehment to gutter length.
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Prepared from CDIRS by: Hydrometeorological Advisory Service, Melbourne
© Commonwealth of Australia, Bureau of IVIeteorology, 1991
FIGURE E4 AREA 2— RAINFALL INTENSITIES (mm/h)— 5 MIN— ARI 20 YEARS
TjT^-7-7-7 / / 77 7 7
''' mfyiTi - /j-jsy::/ :z-/: .
/ / rHJ-- 1- / / / '-7- ^^
::X'-N llIti^uI/^j / 7 7
I IJ iL Zu7 / 7 -7-y-y-'- ^
-'--Ijr rriJ'f^^ 7 7 7"~^7'~
r Tij 7 / 7 iMt-- / 7 :
::7'^A^//t2^7 777 F3^- 1^^:;-^
11 Jj// /7/7-Z7-7r-z.,..^..
UJil// 7 7/7 /y /a?-' z\
::tp2,L/777yy7:-77'7z:m^^
t '17)7 / 7 77/ /_X^Z ^^.-^7.
mM7///A-z777Z7-^\_ 7
1// / 7777/7 y7-<-K7Z--' \
/ 7 7/y7Z Z-'7^'' ^^t^"'' \
77777lk7ZZ'7'7'' \
z^;;;^^^ J^^^2^^^^ i>i 'iifih liAiN Ai iMi'.M;rv
y ^^ ^'^Ty'^^^''^ 1^%' 3R l'"/iol. ''^"■'fi (' Vl-^IOAI.)-^
gggs^'l
i -
4 f.i G / /.! 9 10 n 1? 33 14 11. 16 1/ 10 19 I'O ill :■;> ;'3 .-14
Lll-CnVi: CnOSR miCTfONAi AUr-IA or i;AVi:0 GUfll (■ lA^i. 1U0U (nrn'"
roi? GlMi:iir-Nii3 or iilait!-:;? ihan i : fioo
i. 1 -1 1...1 1 1 1 —J — : — \ — 1. -1 1....1, -1 — 1 i_u..,i III
TOTAL FLOW IN EAVES GUTTER (L/s)
NOTES:
1 This graph assumes —
(a) an elTecLive width to depth is a ratio ofabout 2:1;
(b) a gradient in the direction of How of Hatter than 1 :500;
(e) the least favourable positioning of the downpipe and bends within the gutter length;
(d) a cross-section or half round, quad, ogee or square; and
(e) the outlet to a vertical down pipe is located centrally in the sole of the eaves gutter.
2 The required eaves gutter discharge areas do not allow for loss of waterway due to internal brackets.
FIGURE H4 APPLICATION OF FIGURE 3.5(B)
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DP-B
DP-E
15
4.25
DP-D
DP-C
_l L I 1
10 m
J I ^1
Total catchment between DP-D AND DB-A (clockwise) = 72 nn^
Catchnnent area for DP-E = 36 nn^
FIGURE H5 ROOF PLAN— CASE 2
H2.3.2 Solution
Adopt the following:
(a) Roof plan as shown in Figure H3 with eaves gutter gradients for Case 2 flatter than
1:500.
(b) Eaves gutters with an effective cross-sectional area of 7300 mm^.
(c) Vertical downpipes of 85 mm diameter or ] 00 mm x 50 mm.
(d) Minimum height of fascia above gutter overflow is 18 mm.
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APPENDIX 1
BOX GUTTER SYSTEMS— GENERAL METHOD, DESIGN GRAPHS AND
ILLUSTRATIONS
(Normative)
Figures 11 to 18 of this Appendix apply, within the limitations of Clause 3.7. 1, to the
general method (see Figures 3.9, 3.10 and 3.1 1) for the design of solutions for —
(a) box gutters, see Figure H; and
(b) rainheads, see Figures 12 and 13; or
(c) sumps with either side overflow devices, see Figures 14, 15 and 16 or high-capacity
overflow devices, see Figures 17 and 18.
NOTE: Applications of this Appendix are illustrated by Examples 1, 2 and 3 given in Appendix J.
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Design flow [Q]. L/s
S E
^_,
^
i±
<D
■n
u
CO
F
o
~i
SJ
E
cu
400
2
'■
J L
I t
) e
/
^
\ c
) 10 11 12 13 14 15 M
/
/
/
/
/
/
360
/
y
/
/
/
A
/
1
/
/
/
/
/
"to
■^ 320
CD CM
/
/
/
/
/
/
l\
/
/
/
-/
/
/■
> E
^~ 280
CD Q
1
1
/
/
/
/
/
/
/
/
/
/
/
/
V
S g. 240
/
j
/
/
/
/
/
/'
/
/
h
k
/
r/
^i
/
/
/
/
^
c 5
CD o 200
E -o
/
#/^
/
y
/
/
/
/
/-
/^
/
.^
y
^
^
^
o
5 ^^^
/
//
7
/
X-"
y
//
/
/
A
/
>
/
>!"
^^
k-
.^^
^
120
/
//
7
/
f /
/
/
^
^x
//
V/
V
/
/
y
^
^m-;]
Minimum depth of box gutter
discharging to rainhead 80
including freeboard [h^] with
slope adjustment in mm
170 150 130 110 90 ^^
h
'/.
//
/
/
^
/
^
;;;;^
.-^
^^§0
1
^
/
^
^
^>"
^
^
^
^
=^
^^
i
\
— '
vC
J
80
■ /
7
//
100
//
^
X
®
^
y
sX
:^
^
^
120
/>
f \
\
^
^
^
\^
^
\^
/
/
\,
\
N
\
^
•->^
"^
140
vA
/
^
^
^1
\
\
\
s
\
-^nn
'^
A
\
\
N
\
'\j
X
\
^
->
160
/
:i^C^:
T^^
^
/
\
s
k^
/
^
1 1 11 n
o o oo
-O lO o^
rsj -^ ^
\
\
s
\
\
fe
180
/
7)
\,
\
Sw,?^
^
/.
V}
/ /
T- T- T-T-
^•^c
t
T^
900
/
"
X
N
400
360
320
CD
CD
C3.
CO
Q.
, ,
C
c
^
CD
o
b
ID
o
CDfNj
> E
280 -„
240
200
160
120
80
40
80
100
120
140
160
180
200
170 150 130 110 90 70 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Minimum depth of box gutter discharging
to rainhead including freeboard \h^] with
slope adjustment in mm
Design flow (0). L/s
C3)
^ E
"^ e
o ^
E c
CD
~™^
S. fD
s-S
Cl
(D -o
CO
LEGEND:
@= Design rainfall intensity (^°°/^) or {^°/^q) in mm/hr (typical)
(b) = Width of box gutter \w^^^ in mm (typical)
(c) = Gradient of box gutter (typical)
NOTE: 200 mm box gutter J or domestic construction only.
FIGURE 1 1 DESIGN GRAPH FOR A FREELY DISCHARGING BOX GUTTER
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hr - 25
NOTES:
1 This ilgure applies for h^>\25 D^ or 1 .25 D[
2 For h,. and /,., see Figure 13.
3 Width of rainhead is equal to the width of box gutter.
4 The rainhead to be fully sealed to the box gutter and the front of the rainhead left open above the overHow weir.
FIGURE 12 RAINHEAD
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Approximate
water profile with
blocked downpipe
The minimum gradient for overflow
duct or channel, with lengths —
(a) equal to or less than 450 mm,
is horizontal; and (b) greater than
450 mm, is 1 : IO-7
^/•/^7Z7- /y 77 yy 7V -
/
dr,n min.
(a) Section showing overflow duct or channel
Approximate water profile with blocked downpipe
77 7/ '7/~yy^r7/~j/-'//-~//^/y~/—//"/~/TV7^rr/T)(zr.
I
/oc+ (c/oc + 30) min.
1
Sole of box gutter
^ Overflow duct ^
or channel
r /T i 77 77 77 77 -/7 ^V—7"7/^/-7/-7^-/Z"/ 7-/7-77^/7-/7"" 7Z 77 77'
/oc rnin.
Sump
Downpipe
'- — 0.7 /qc t^'n-
/oc min.
Minimum gradient of box gutter, 1:200-
-Minimum length of sump (h/qc + 2/oc) ~ ^00 mm
(b) Side view of box gutter
NOTE: The sump and overHow channel to be fully sealed to the box gutter.
DIMENSIONS IN MILLIMETRES
FIGURE 15 SUMP/SIDE OVERFLOW DEVICE
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70
60
50
40
30
LL
O
CO
LU
3
< 20
10
Width
Of t
ox gi
jtter
t^bgt'
mm
1
(typical) —
'Z^
300^
"'
^
375_^
A50^
^00^
^
--
5
^
^
"^
J,"^"'^ ^.^
==
-^
^^^^
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
LARGEST DESIGN FLOW OF ANY ONE BOX GUTTER L/s
(a) Determination of values for /^p
180
u. ^° 120
O —
tr ^ 100
O 80
60
40
-200
Width of overflow channel (h^q^), rnm (typical) — -
-"■''"'"'■""'"
^...--^
"3 00-
^.^--^
,,.:.,;.>--^
,->^
„...---
^^.^
450
"'^ 1
J
^^
^^^^^^
^^^.^
^^^^
^
""^
^
-^
----^
^^..^^
.^^^
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
TOTAL DESIGN FLOW FROM EACH GUTTER AND SECTION OF ROOFING L/s
(b) Determination of values for d^^
NOTE: Graph (a) applies to both sump/side overilow device, and sump/high-capaeity overllow device.
FIGURE 16 DESIGN GRAPH FOR SUMP/SIDE OVERFLOW DEVICE
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150
Box gutter -
i
-Overflow downpipe
-Normal downpipe
^bg
T
200
B
^
200
Sump
200
T
(a] TOP VIEW
-Approximate water profile with blocked downpipe
A
■ 77 '7? //'// /
h,
\ Sole of
'^bg I Crest of overflo
box gutter 1 /qc I^ *<dX
_^ r\
ZT zr 7z v? 7? 77 V? ^/~/~/~^r7/^/.^/;^/?~y7'~/T r/' zr rr/.
w weir
Sump
Am
-45
max.;
Minimum gradient of box gutter, 1:2 00-
Overflow downpipe
(b) SECTION A-A
40 upstream sole of overflow channel
Crest of overflow weir
60 downstream sole of overflow channel
Normal downpipe
(c) SECTION B-B
NOTES:
1 The depth of the sump {h^ is measured —
(a) if /^,t. >60, from the sole of the box gutter at the sump; or
(b) if /oc <60, the downstream sole of the overnow channel i.e., 60 - /^c below the sole of the box gutter at
the sump.
2 The sump to be fully sealed to the box gutter.
3 See Clause 3.7.5 for criteria for over Row devices.
4 The normal outlet may be moved longitudinally to enable better inspection and maintenance access (see
Clause 3,7.4(1)).
DIMENSIONS IN MILLIMETRES
FIGURE 17 SUMP/HIGH-CAPACITY OVERFLOW DEVICE
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40
130
120
110
100
E
E
LL
O 90
00
UJ
Z)
_J
<
>
70
60
50
WIDT
H OF
A BC
X GU
TTER
(i^bgl
mm
-300/
/
^
375,
/
y
y
/^
45 0/
525/
600^
^
/
/
y
^
X
^
/
>
/
y
^^
^
/
/
^
y
y.
<
^
^
^
^
y.
^
^
3 4 5 6 7 8 9 10 11 12 13 14 15
LARGEST DESIGN FLOW OF ANY ONE BOX GUTTER L/s
NOTE: Additional values can be calculated using the formula— (} = A^ x '^^^/5/3600
16
FIGURE 18 DESIGN GRAPH FOR SUMP/HIGH-CAPACITY OVERFLOW DEVICE
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APPEMDIX J
BOX GUTTER SYSTEMS^GENERAL METHOD—EXAMPLES
(Informative)
Jl SCOPE
This Appendix sets out examples that illustrate the application of the general method (see
Clause 3.7) for the sizing of solutions for the fbilowing:
(a) Example 1 — Box gutters, rainheads and downpipes.
(b) Example 2 — Box gutters, sump/side overflow devices and downpipes.
(c) Example 3 — Box gutters, sump/high-capacity overflow devices and associated
vertical downpipes.
The calculations are presented in an explanatory form to assist first and occasional users.
The adopted order of accuracy in the examples is consistent with the accuracy of the
assumptions on which they are based.
NOTE: Appendix D gives guidelines for the determination for any place in —
(a) Australia, of rainfall intensities for 5 mins duration and ARIs of 20 and 100 years; and
(b) New Zealand, of rainfall intensities for 10 mins duration and ARIs of 10 and 50 years.
J2 EXAMPLE 1: BOX GUTTERS, RAINHEADS AND DOWNPIPE
J2.1 Problem
A building as shown in Figure Jl is to be constructed at Doncaster, a suburb of Melbourne,
Victoria (see Figure E7). Determine the size of the box gutters and associated vertical
downpipes with rainheads that are to discharge to the site stormwater drains of the surface
water drainage system.
To assist the understanding of this example the application of Figure 11 and 13 is shown in
Figure J2.
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Wall-
Rainhead
Downpipe
FIGURE J1 BUILDING PLAN
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Design flow (O). L/s
150 130 110 90 70 1 2 3 4 5
7 8 9 10 11 12 13 14 15
Minimum depth of box gutter discharging
to rainhead Inciuding freeboard [h^] with
siope adjustment in mm
Design fiow (O). L/s
FIGURE 11 REQUIRED SIZE OF BOX GUTTER DISCHARGING TO A RAINHEAD
(a) Application of Figure 11
7 6 9 10 11 12
DESIGN FLOW (0 1 , L/s
120 160 200 240 280
100 140 180 220 260 300
LENGTH OF A RAiNHEAD ( /r I , mm
FIGURE 13 DESIGN GRAPH FOR RAINHEAD
(b) Application of Figure 13
(The Figures above have been reprodueed in reduced size for the purpose of this example only.
Use Figures in Appendix 1 when designing or checking components of box gutter systems.)
FIGURE J2 EXAMPLE 1— APPLICATION OF FIGURES 11 AND 13
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J2.2 Calculation
The calculation below illustrates the application of the procedure shown in Figure 3.8. Each
step designation (for example (b)) has a corresponding letter in the flow chart. Proceed as
follows:
(a) From Table 3.1, select 100 years ARI for Australia, and 50 years ARl for New
Zealand.
(b) The latitude and longitude of the site at Doncaster (Melbourne), Victoria are 37.8°S
and 145.2°E.
From Figure E7, the five minutes duration, 100 year ARl rainfall intensity for the
given latitude and longitude is 178mm/h. Take this as 180mm/h. Hence
''V5- 180mm/h.
(c) The dimensions and other relevant data are shown on Figure Jl.
(d) Select position of expansion joint and rainheads as shown in Figure Jl.
(e) Refer to Figure 3.9(b).
Roof//h= 14.5 m X 18 m-261 m\
Roof slope 1:6. Rise = 1/6 x 18 m == 3 m.
Roof ^vi = 14.5 m X 3 m = 43.5 ml
WalMv2 = 14.5 m x 8.8 m
= Ml, 6 m^
^c-A + ^/2(^V2-yivi)
A, - 261 m- + V2 (127.6 - 43,5)m^
A, - 303 m^
(f) From (b), "V5 = 1 80 mm/h. From Step (e) A^ = 303 mml
From Figure 1 1 , g = 1 5 L/s.
(g) Is the design flow g > 1 6 L/s.? No. Go to Step (h).
(h) From Figure 11, for g= 15 L/s, select sole width of box gutter (Wbg) "^ 450 mm and
gradient = 1 :200.
(i) From Figure II, for Q = 15 L/s, w^g "^ 450 and gradient = 1 ;200, the actual minimum
depth of box gutter including freeboard (/?a) "^ 140 mm.
As each box gutter discharges to a rainhead that is designed to divert the design How
away from the building in the event of a total blockage of the downpipe, without
increasing the depth of flow in the box gutter, this is the minimum depth required for
the box gutter.
Use box gutters 450 mm x 140 mm minimum with a gradient 1 :200.
(j) The design flow in each box gutter is also the design flow in the rainhead. From
Step(f), e== 15 L/s.
Select 125 mm diameter downpipe. From Figure 13, depth of water in
rainhead = 207 mm, total depth of rainhead /?, = 345 mm.
Alternatively, select 150 mm x 100 mm downpipe. From Figure 13, depth of water in
rainhead = 144 mm, total depth of rainhead /?i ^ 240 mm. Use total depth of
rainhead = 250 mm.
(k) Check if the total depth h^ needs to be adjusted as required by Note 1 of Figure 12
RAINHEAD.
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(I) From Figure 13, for h,y= 140 mm, length of rainhead {l,) = 185 mm (use 200 mm), and
total depth of rainhead {h^) = 250 mm.
(m) Refer to Figure 12 and Figure 3.7(a). Final dimensions of rainhead, /z, = 250 mm,
/2, - 25 = 225 mm, h.^ = 1 50 mm. /, = 200 mm.
J3 EXAMPLE 2: BOX GUTTERS, SUMP/SIDE OVERFLOW DEVICES AND
DOWNPIPES
J3 1 Problem
A building as shown in Figure J3 is to be constructed in Brisbane, Queensland (see
Figure E3). Determine the size of the box gutters and the associated vertical downpipe with
sump/side overflow device that is to discharge to the site stormwater drains of the surface
water drainage system.
To assist the understanding of this example the application of Figures 14 and 16 is shown in
Figure J4.
0,3 m
FIGURE J3 ROOF PLAN
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1 1 J 1
Wldlh o( box guMor
iM-bal. "im {typical) --
-^
300,
60
■375;
^^
i 50
^
^-^
450
^^-^
•^
_^
--^
525,
J 40
u.
O
< 20
10
n
^
^
^-^
^
H ■
Soo,
•^
^
;;:::::
-^
::==
"^
--
-■
--
b:;
^
^
^
^
r"
r
'^
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
LARGEST DESIGN FLOW OF ANY ONE BOX GUTTER L/s
(a) Determination of values for /^p
5 160
...-»-
200
Width of overflow channel dTj^,), mm (typical)
■"^""
-r"
300-
"^so"""
^"
_"-_-
— ■-
-_ -
- —
-^
■ — '
0"o
%
^
•^ — '
X nJ
^ 1 loo
^
^
_^____,
^
...^
° I
1 80
1 60
„^^i^
,.>'^
^ ■
-^
^^
^
^.
^0-^
^^
> 3 4 5 6 7 8 9 10 11 12 13 14 15 16
TOTAL DESIGN FLOW FROM EACH GUTTER AND SECTION OF ROOFING L/s
(b) Determination of values for gL
FIGURE 14 DESIGN GRAPH FOR SUMP
FIGURE 16 REQUIRED SIZE OF
SUMP/SIDE OVERFLOW DEVICE
(al Application of Figure 14 (b) Application of Figure 16
(The figures above have been reproduced in a reduced size for the purpose of this example only.
Use Figures in Appendix I when designing or checking components of box gutter systems.)
FIGURE J4 EXAMPLE 2 —APPLICATIONS OF FIGURES 14 AND 16
J3.2 Calculation
The calculation below illustrates the application of the procedure shown in Figure 3.9. Each
step designation (for example Step (b)) has a corresponding letter in the flow^ chart. Proceed
as follows:
(a)
(b)
(c)
(d)
(e)
From Table 3.1, select 100 years ARI for Australia, and 50 years ARI for New
Zealand, for box gutters with a normal factor of safety.
From Figure D3, the 5 min duration, 100 year ARI rainfall intensity ('^^^^/s) for
Brisbane is 330 mm/h.
The dimensions and other relevant data are shown in Figure J3.
Expansion Joints are installed at 10 m intervals along the box gutter near the parapet
with sumps and downpipes midway between the expansion joints (see Figure J3).
With reference to Figure 3.9(b), the parapet 300 mm wide directs rain falling on top
surface into the box gutter. Therefore, include as catchment area (see Clause 3.4).
Length of roof + parapet = 16.9 m.
Roof ^1, - 5 m X 1 6.9 m - 84.5 ml
Roof slopes at 1 : 10.
Roof rise == 1/10 x 16.6 m = 1.7 m.
Roof//
v2
5 m X 1.7 m = 8.5 m ,
Parapet A^\ = 5 m x 1 m == 5 m^.
COPYRIGHT
AS/NZS 3500.3:2003 158
Ac = A/, + V2(Ay2-AM)
//, - 84.5 + '/2(8.5m^-5m^)
Ac = 86.3 m^-
(f) From (b) '^^^5 = 330 mm/h. From Step (e), A, = 86.3 mml
From Figure 11, ^ ^ 8 L/s for each gutter.
(g) Sole width ^ 600 mm, gradient of box gutters = 1 :200
(h) Is the total design flow through the outlet Q> 16 L/s? No. Go to Step (i).
(i) Are the gradients of the box gutters flatter than 1 :200? No. Go to Step (j).
(j) Total design flow = 2x8 - 16 L/s. Select 150mm diameter downpipe. From
Figure 14 and 15, h^ = 220 mm.
(k) For either box gutter Qmux- ^ 8 L/s. From Figure 16(a), /oc ^ 26 mm.
(1) Select width of overflow weir Woc - 300 mm.
(m) Total design flow = 16 L/s. From Item (1), H^oc = 300mm. From Figure 16(b),
doc = 132 mm. From (/:), /oc = 26 mm. h, = (/oc + (doc + 30)) - (0.7 /oc) = 1 70 mm.
Alternatively, if Woc =" 450 mm. From Figure 16(b) d^c "= 102 mm, h^ = 140 mm.
(n) From (k), /oc = 26 mm. For h^oc - 300 mm, ^i^g = /^c + (doc + 30) =^ 1 88 mm. For
Woe ="450 mm, ^bg "^ /oc + (^oc + 30) = 158 mm. Select appropriate option, say
d\,„ = 1 88 mm. Go to (o).
(o) Refer to Figure 15 and Figure 3.7(b). Sump details. From Step (j), depth of sump
hs = 220 mm. Width of sump = Woc + 2 /oc = 300 + 2 x 26 =^ 352 mm min. This is less
than the allowable minimum of 400 mm (Figure 15). Use 400 mm.
Overflow duct details. For Woc ^ 300, c/oc ^ 132 mm. Hence, overflow duct opening
300 mm X 132 mm for depth of box gutter = 188 mm. Bottom edge of duct
0.7 X 26 = 1 8 mm above sole of gutter.
J4 EXAMPLE 3: BOX GUTTERS, SUMP/HIGH-CAPACITY OVERFLOW
DEVICES AND DOWNPIPES
J4.1 Problem
A sump/high-capacity overtlow device is to be fitted to the outlet of 5.0 m long and 3.8 m
long box gutters with gradients of 1:200 and sole widths of 600 mm. Inflow from the
catchment area of the roof is at the rate of 1 .7 L/s/m. Determine the size of the box gutters
and the sump/high-capacity overflow device including the normal and overflow vertical
downpipes.
To assist the understanding of this example the application of Figures 14, 16(a) and 18 is
shown in Figure J5.
COPYRIGHT
159
AS/NZS 3500.3:2003
N
D
(1
OM
F
YP
IC/
L
IPE
\L)
E
m
\
iia.
/
10
;
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75
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10
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5 (
IS
ia.
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00
f\
26 X
40 die
hi-
dia.
25
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-
-
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1.
/
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/
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2 3 4 5 6 7 e 9 10 11 12 13 U 15
DESIGN FLOW (O) L/s IN DOWN PIPE
^
— ^
width
- 1
ol box gutter
■«^g
,..
i
(typical) -
— ■
^
300,
^
^
s:
^
^
^
^
--
--
--
<^
^
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^
I
1
1
1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
LARGEST DESIGN FLOW OF ANY ONE BOX GUTTER L/b
(a) Determination of values for Ln
FIGURE 14 DESIGN GRAPH FOR SUMP
FIGURE 16 DESIGN GRAPH FOR
SUMP/SIDE OVERFLOW DEVICE
(a) Application of Figure 14
(b) Application of Figure 16
FIGURE J5 (in part) EXAMPLE 3— APPLICATION OF FIGURES 14, 16(a) AND 18
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AS/NZS 3500.3:2003
160
O 90
WIDT
H OF
A BC
X GU
TIER
fWbg)
mm —
—
—•■"
y
300^
V
/
/
>
/-
/
/
y
y
y
/
450^
/
y
y
y
/
^
525^
/
/
/
/
X
^
^
/
^
y
/
6
■4
y
^
'f
^
^
^
^
3 4 5 6 7 8 9 10 11 12 13 14 15 16
LARGEST DESIGN FLOW OF ANYONE BOX GUTTER L/s
FIGURE 18 REQUIRED SIZE OF SUMP/HIGH-CAPACITY OVERFLOW DEVICE
(c) Application of Figure 18
FIGURE J5 (in part) EXAMPLE 3— APPLICATION OF FIGURES 14, 16(a) AND 18
TABLE Jl
DATA FOR EXAMPLE 3
Depth of box
Item
Length
Design flow
gutter with
discharge to
rainhead (/i^)
from Figure It
Width
m
L/s
mm
mm
Box gutter
(a)
5.0
8.5*
(1.7x5.0)
105
600
(b)
3.8
6.5
(1.7 X 3.8)
98
600
Sump
0.6
(see Figure 17)
1.0
(1.7 xO.6)
" — ■
—
lolals
9.4
16.0'
—
—
* Largest design flow from any one box gutter.
■ Total design flow from each box gutter and section of roofing.
COPYRIGHT
Al
AS/NZS 3500.3:2003
J4.2 Calculation
The calculation below illustrates the application of the procedure shown in Figure 3.10.
Each step designation (for example (b)) has a corresponding letter in the flow chart.
Proceed as follows:
(a) From Table 3.1, select 100 years ARl for Australia, and 50 years ARI for New
Zealand, for box gutters with a normal factor of safety.
(b) (Steps (b) to (g)). The procedure for the determination of the catchment areas and
design flows is illustrated in Appendix J, Examples 1 and 2. The procedure for the
determination of the minimum depth of box gutter (h^) for free flow conditions is the
same as for a box gutter served by a rainhead shown in Example I. Table J 1
summarizes the results of these procedures for a selected width of box gutter (wbg) =
600 mm.
(c) Is the total design flow through the outlet >1 6 L/s? No. Go to Step (i).
(d) Select 1 :200 min. gradient of box gutters. Go to Step (j).
(e) Total design flow = 16 L/s. From Figure 14, for a 150 mm diameter downpipe, the
depth of sump (/zg) = 217 mm. Adopt 220 mm.
(f) gmax. = 8.5 L/s for any box gutter. Width of box gutter = 600 mm. From
Figure 16(a), l^c = 27 mm.
(g) If the downpipe ceases to function because of a blockage, the water level at the ends
of the box gutters will increase to discharge the design flow across the overflow
weirs. From Table Jl, the largest flow in any box gutter is Q = 8.5 L/s. From
Figure 18, for Q = 8.5 L/s and Wbg = 600 mm, the minimum height of the box gutter
above the top of the overflow weirs (hi) = 83 mm.
(h) The depth of box gutter has to be sufficient to contain the flow under overflow
conditions without overtopping. Usually, the minimum total depth of gutter (dy,^)
required for this condition is more than the minimum total depth of gutter (/z-i)
required when there are no blockages. But for wide gutters this is not always the case,
partly because of different levels of freeboard incorporated in the graphs.
From Step (g) (shown on summary Table Jl), //a = 105 mm. From (1), h^ = 83 mm.
From (k), /^^j; = 27 mm. /z, + /oc = MO mm.
Is h,(105) < //i + /oc (110)? Yes. Go to Step (n).
(i) The minimum depth of box gutter J^g ^ h + /oc = 1 '0 mm.
Cj) Is /oc >60? No? Go to Step (p).
(k) The datum level for depth of the sump is the sole of the box gutter.
(1) Refer to Figure 17. Sump details. From Step (j), depth == 220 mm minimum below sole
of gutter. Length ^ 600 mm. Width = 600 mm.
Overflow weirs. From Step (k), crest of weir above sole of gutter == 27 mm.
From Step (n), depth of box gutter =110 mm minimum.
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AS/NZS 3500.3:2003 162
APPENDIX K
SURFACE DRAINAGE SYSTEMS^NOMINAL AND GENERAL METHODS-
EXAMPLES
(Informative)
Kl SCOPE
This Appendix sets out examples that illustrate the application of the nominal method (see
Clauses 5.5) and the general method (see Clause 5.4) for the design of solutions for surface
drainage systems.
The calculations are presented in an explanatory form to assist first and occasional users.
The adopted order of accuracy in the examples is consistent with the accuracy of the
assumptions on which they are based.
NOTE: Appendix D gives guidelines for the determination for any place in —
(a) Australia, of rainfall intensities fbr five minutes duration and ARIs of 20 and 100 years; and
(b) New Zealand, of rainfall intensities for 10 minutes duration and ARIs of 10 and 50 years.
K2 EXAMPLE 1: NOMINAL METHOD
K2.1 Problem
A house on an urban allotment with an area not exceeding 1 000 m^ as shown in Figure Kl
is to be located in Australia. Design the surface drainage system constructed with non-metal
products.
K2.2 Solution
K2.2.1 Layout
The layout of the surface drainage system shown, which is in Figure Kl, shall comply with
Clause 5.3 and have the site landscaped so that the overland flow path is directed away
from the building, e.g., the cross-fall of a paved path along rear of the building is to be
away from the building.
K2.2.2 Site stormwater drains
For the site stormwater drains —
(a) the minimum size, determined from Clause 7.3.4 is —
(i) between a downpipe outlet and a stormwater or inlet pit, DN 90;
(II) between the stormwater, pits A and B, DN 1 50; and
(iii) between pit B (see Clause 8.6.1 .2(b)) and the street kerb, two DN 1 00;
(b) the minimum cover, determined from Table 7.1 is —
(i) within the property —
(A) other than under the driveway, 100 mm; and
(B) under the paved driveway, 75 mm below the underside of the pavement;
and
(ii) outside the property under the paved footpath, 50 mm below the underside of
the pavement; and
(c) the minimum gradient, determined from Table 7,2 for Australia, is DN 90, DN 100
and DN 150, 1:100.
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163 AS/NZS 3500.3:2003
K2.3 Stormwater pits
For stormwater pits —
(a) the minimum internal dimensions, determined from Table 8.2, are at A and B,
450 mm x 450 mm (depth to invert of outlet less than 600 mm).
(b) the minimum fall across each pit is 20 mm (see Figure 8, 4(a)),
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AS/N/.S 3500.3:2003
164
Kerb line
Exit to street kerb
Footpath
QI
Grated drain
fv.I|2 X DN 100
il]
Junction
DN 150
DN 90
Pit B
Fall of land /
/ /
/
/ Overland flow path
. allowing for possible
/ flows from adjoining
/ properties
/ 16
5 m
1 I I I I I
Scale
LEGEND;
Downpipe, outlet
Stormwater pit
Site stormwater drain
DIMENSIONS IN METRES
FIGURE K1 STORMWATER DRAINAGE INSTALLATION PLAN— EXAMPLE 1
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165 AS/NZS 3500.3:2003
K3 EXAMPLE 2: GENERAL METHOD— VILLA HOME DEVELOPMENT
K3.1 Problem
A three-unit villa home development is to be located in Melbourne, Victoria, on a property
with an area of 912 m^ (48 m x 19 m) as shown in Figure K2. The property slopes away
from the street, and since there is some risk of flooding of the garage for Unit 3, a grated
drain is provided in front of this. For the same reason, an ARl of five years should be
adopted for the sizing of the surface water drainage system.
K3.2 Assumptions
It is assumed that there is little chance of overflows from the street gutter coming through
this property. However, the site drainage path has to be well established, with any
overflows being collected in pits or directed beside buildings to the easement drain running
through the lower part of the site. Specifically, there should be gaps under fences adjacent
to Pits 2 and 4, so that any overflows can escape without ponding against fences.
Roof water is collected from the vertical downpipes. Each downpipe for the villa house can
be assumed to drain 25% of the associated roof. Downpipes on garages can be assumed to
collect all of the rainwater from a roof plane.
It is assumed that the paved areas will be reinforced concrete and be capable of taking
medium vehicle loads. Thus cover depths can be small — a minimum of 100 mm below the
pavement (say 200 mm overall) will apply. In courtyards without paving, a cover of
100 mm will be required (see Table 7.1).
K3.3 Solution
K3.3.1 Preliminary
Determine, for an ART of 5 years, values for the following:
(a) The rainfall intensity for a 5 min duration Cls) is 87 mm/h (see Clause 5.4.5(a)).
(b) Assuming loam soils, the run-off coefficient for the un-roofed pervious area (Cp) is
0.147 X 0.95 = 0.14 for a '^50 of 28.6 mm/h (see Equation 5.4.6 in Clause 5.4.6(a)).
K3.3,2 Procedure
A trial surface water drainage system is shown in Figure K2. In this case, it is most
convenient to establish this as two subsystems, running on either side of the lower Unit 3.
Plastic pipes are assumed to be used, having a roughness coefficient k= 0.0X5 mm (see
Table 5.6).
Table Kl can be set up on a spreadsheet program that enables the automatic determination
of the values shown in the shaded areas. The column numbers below refer to Table Kl :
Column 1 — identifies the limits for each section of the site stormwater drain.
Column 2 — gives for each section the length.
Columns 3, 4 and 5 — give the catchment area for each section, respectively, for the
upstream —
(a) root^ the plan area irrespective of the roof slope;
(b) unroofed impervious (paved) area; and
(c) unroofed pervious area.
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AS/NZS 3500.3:2003
166
Kerb
Grated drain
and pit 2
27.5
Footpath
DP14 DP13
iPitV^"^^"^-^^-
/
Courtyard
Junction J2/
-^
29,0 AHD
Fall ot land
- 28.5
5 m
1 1 I I I I
Scale
48
28.0
DP11
DP12
Easement or inter-allotment drain
LEGEND;
Downpipe, outlet
Stormwater pit
Site stormwater drain
i
DIMENSIONS IN METRES
FIGURE K2 STORMWATER DRAINAGE INSTALLATION PLAN— EXAMPLE 2
COPYRIGHT
TABLE Kl
CALCULATION SHEET— EXAMPLE 2
o
o
o
X
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Conduit
Length
Roof
area
Paved
area
Pervious
area
Equivalent
impervious area m
Design
flows
Pipe
diam.
Pipe
gradient
Pipe
capacity
Full-
pipe
velocity
Min. fall
across
U/Spit
U/S
surface
level
D/S
surface
level
U/S
invert
D/S
invert
Cover
ni
m
m^
m^
m^
Sub-
catchment
Cumu-
lative
L/s
mm
1:...
0.015 mm
(L/s)
m/s
m
m
m
m
m
U/S
pipe
end
D/S
pipe
end
DPI to Pit 1
14.2
26
26
26
0.6
90
25
12
0.10
NA
28.95
28.55
28.61
28.04
0.25
0.42
DP2 to Pit 1
5.7
26
26
26
0.6
90
21
14
0.10
NA
28.60
28.55
28.31
28.04
0.20
0.42
Pit ] to n
19.4
96
64
95
147
3.6
150
67
28
0.20
0.02
28.50
28.25
28.02
27.73
0.33
0.37
DP3 to Jl
6.9
26
26
26
0.6
90
25
12
0.10
NA
28.30
28.25
28.01
27.73
0.20
0.43
.n to Pit 2
11.5
173
4.2
150
25
48
0.24
NA
28.25
27.80
27.73
27.27
0.37
0.38
DP4, DPS to Pit 2
7.1
52
52
52
1.3
90
24.5
12
0.20
NA
27.85
27.80
27.56
27.27
0.20
0.44
Pit 2 to Pit 3
10.2
154
21
142
367
8.9
150
25
48
0.50
0.02
27.80
27.45
27.25
26.84
0.40
0.46
DP13toDP14
41
41
41
1.0
90
67
7.5
0.16
NA
27.55
27.53
27.26
27.26
0,20
0.18
DP14toPit3
2
15
15
56
1.4
90
20
14
0.21
NA
27.53
27.45
27.20
27.10
0.24
0.26
DP6 to DP7
13
26
26
26
0.6
90
25
12
0.10
NA
29.00
28.60
28.71
28.19
0.20
0.32
DP7to DPS
4
41
41
67
1.6
90
25
12
0.25
NA
28.60
28.45
28.19
28.03
0.32
0.33
DPS to DP9
4
30
30
97
2.3
90
33
11
0.37
NA
28.55
28.35
28.03
27.91
0.43
0.35
DP9 to Pit 4
12
41
41
138
3.3
90
25
12
0.52
NA
28.35
27.90
27.91
27.43
0.35
0.38
Pit 4 to DPI!
1.4
26
102
40
178
4,3
150
33
40
0.24
0.02
27.90
27.90
27.43
27.39
0.32
0.36
DPI! toDP12
8
26
26
204
4,9
150
33
40
0.28
NA
27.90
27.60
27.39
27.15
0.36
0.30
DP12to J2
3
26
26
230
5.6
150
33
40
0.31
NA
27.60
27.55
27.15
27.06
0.30
0.34
Pit to easement
73
10
29
0,7
—
—
—
—
27.45
—
—
—
—
—
Sums =
LEGEND:
U/S = upstream
D/S = downstream
NA = not applicable
402 250 260
Total area = 912 m-
AS/N/.S 3500.3:2003 168
Column 6 — gives for each section the equivalent impervious area calculated from the
following equation:
SCM = C,A, + C, 4 Hh Cp^p ... K3 .3 .2( 1 )
where
Y.CA ^ equivalent impervious area of all upstream areas on the property, in
square metres
C, = run-off coetYicient, for a roofed area
Ay = total roofed catchment area, in square metres
Ci = run-off coefficient for an unroofed impervious (paved) area
Ai = total unroofed impervious (paved) catchment area, in square metres
Cp = run-off coefficient for an unroofed pervious (paved) area
Ap = total unroofed pervious catchment area, in square metres
In Australia, C, and C, are equal to 1.0 and 0.9, respectively (see Clause 5.4.6), and for
Example 2 Cp is equal to 0.14 (see Paragraph K3.3.1(b)).
Column 7 — gives for each section the cumulative equivalent impervious area (see Column 6
and Figure K2). This has to be determined by the designer, allowing for branching.
Column 8 — gives for each section the design flow calculated from the following equation
(see Clause 5.4.8 and Equation 5.4.8):
. . . K3.3.2(2)
Q-
XCA'I,
3600
where
Q
= (
HCA
= (
%
= I
design flow, in litres per second
equivalent impervious area of all upstream areas on the property, in
square metres
rainfall intensity tbr a duration of five minutes and an ARl of five years,
in millimetres per hour
Column 9— gives for each section the selected minimum pipe diameter (see Clause 7.3.4).
Column 10 — gives for each section the pipe gradient (see Clause 7.3.5) determined from
Figure K2 and the minimum cover (see Clause 7.2,6).
Column 11 — gives for each section the hydraulic capacity of the pipe determined from
Figure 5, 1(a) for the selected diameter (see Column 9) and adopted gradient (Column 10).
The hydraulic capacity for each selected minimum diameter pipe is, in this example,
significantly greater than design flow (see Column 8).
Column 12 — gives for each section the full-pipe velocity for the design flow (see
Column 8) calculated from the following equation:
40002 ...K3.3.2(3)
v= ^
\~\d^
where
V ^ full-pipe velocity, in metres per second
Q = design flow, in litres per second
d = diameter of the site storm water drain, in millimetres
COPYRIGHT
169 AS/iNZS 35003:2003
If, for other than steep gradients, the full-pipe velocity exceeds 1.5 m/s select a larger pipe
diameter (see Column 9) and repeat Columns 1 0, I 1 and 1 2.
Column 13 — gives for each pit the minimum fall from the upstream to the downstream
invert levels of 20 mm (see Clause 8.6.3).
Columns 14 and 15 — give for each pit, downpipe outlet and junction the finished surface
level determined in Figure K2.
Columns 16 and 17 — give for each section the —
(a) upstream invert level determined by —
(i) the minimum cover (see Clause 7.2.6); or
(ii) the fall along the immediate upstream section determined from the product of
the length and gradient (see Columns 2 and 10); and
(b) downstream invert level determined by —
(i) the minimum cover as for Item (a) (i); or
(ii) the minimum fall across a pit (see Column 1 3),
provided that the upstream invert levels at —
(A) a junction are the same; and
(B) a pit are, where practicable, the same or the pipe with the higher invert
level drops within the pit.
Columns 18 and 19 — give for each section the upstream and downstream covers determined
from the difference betw^een the relevant surface level (see Columns 14 and 15) and invert
level (see Columns 1 6 and 1 7) less the pipe diameter (see Column 9).
Before proceeding to the sizing of the next section check each cover for compliance with
Clause 7.2.6 and, where necessary, increase the cover, by lowering the corresponding invert
level, to satisfy this requirement.
The minimum internal dimensions of the pits shall comply with Table 8.2.
K4 EXAMPLE 3: GENERAL METHOD— WAREHOUSE
K4.1 Problem
A warehouse building with a plan area of 1344m^ is to be located in Penrith,
New South Wales, on a property with an area of 2482 m" (73 m x 34 m) as shown in
Figure K3. The property slopes to the street.
K4.2 Assumptions
it is assumed that —
(a) overflow from the adjoining properties and Pits A and B will follow the overland
flow path shown in Figure K3; and
(b) the roof of the building falls to the east with the roof water collected at five vertical
downpipes that discharge to the site stormwater drains connected to the street pit with
an invert level of 13.00 m AHD.
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AS/N/S 3500.3:2003 170
K4.3 Solution
K4.3. 1 Preliminary
Determine, for an ARI of two years, values for the following:
(a) The rainfall intensity for a 5 min duration ^Is) is 96 mm/h (see Clause 5.4.5(a)).
(b) The run-off coefficient for the un-roofed pervious area (Cp) is 0.348 x 0.85 = 0.30 for
a '%o of 28.6 mm/h (see Equation 5.4.6 in Clause 5.4.6(a)). To allow for clay soils at
the site, 0.1 is added, so C,, - 0.30 + 0.10 - 0.40
K4.3.2 Procedures
A trial surface water drainage system is shown in Figure K3. The site storm water drains are
to be of FRC pipes, having a roughness coefficient k=QA5 mm.
Table K2 can be set up on a spreadsheet program that enables the automatic determination
of the values shown in the shaded areas. The explanation of the application, but not the
values for Example 2, given in Paragraph K3.3.2 are also applicable to Table K2.
In some cases the pipe diameter (see Column 9) and the cover (see Columns 18 and 19)
could be reduced; however, since the clearance of blockages and replacement of pipes may
be costly the preferred layout is shown in Figure K3.
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AS/NZS 3500.3:2003
Kerb
Street pit
Footpath
IK
Pit C Pit D'
Landscaped area
•.•.•.•.Grated/.V'.-./
'•'■drain •'•It-/ Pit E
^iiiilijuiijijiiiiiiHjriiii'''
Downpipe.'.-.-/^
;:dP5 :::::: Z///^-
14.5 AHD
Fall of land
-15.0
5 lOm
1 I I I I I I I li I
Scale
•15.5
Entry point of overflows ...^--•^Z
from adjoining properties —'""""' /
LEGEND;
Downpipe, outlet -
Stormwater pit =
Site stormwater drain ==
DIMENSIONS IN METRES
FIGURE K3 STORMWATER DRAINAGE INSTALLATION PLAN— EXAMPLE 3
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-<
CD
TABLE K2
CALCULATION SHEET— EXAMPLE 3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Conduit
Length
Roof
area
Paved
area
Pervious
area
Equiva
impervious
ilent
area ni"
Design
flows
Pipe
diani.
Pipe
gradient
Pipe
capacity
Full-
pipe
velocity
Min. fall
across
IJ/S pit
U/S
surface
level
D/S
surface
level
U/S
invert
D/S
invert
Cover
m
m
m^
m^
m^
Sub-
catcliment
Cumu-
lative
L/s
mm
1:...
k=
0.015 mm
(L/s)
M./S
m
m
m
m
m
U/S
pipe
end
D/S
pipe
end
DPI to Jl
16.7
168
168
168
4.5
150
37
34
0.25
NA
15.60
15.35
15.25
14.80
0.20
0.40
DP2to J J
3.8
336
336
336
9.0
150
19.2
50
0.51
NA
15.35
15.35
15.00
14.80
0.10
0.40
Jl to Pit A
15.8
504
13.5
150
50
30
0.76
0.02
15.35
15.15
14.80
14.48
0.40
0.52
DP3 to Pit A
7.1
336
336
336
9.0
150
22
45
0.51
NA
15.15
15.15
14.80
14.48
0.20
0.52
Pit A to Pit B
19.6
403
363
1203
32.1
200
50
62
1.02
0.02
15.15
14.80
14.46
14.07
0.49
0.53
DP4 to Pit B
11.6
336
336
336
9.0
150
22
45
0.51
NA
14.95
14.80
14.60
14.07
0.20
0.58
Pit B to Pit E
20.8
260
234
1773
47.3
225
50
83
1.19
0.02
14.80
14.40
14.05
13.63
0.53
0.54
Pit C to Pit D
19.2
63
25
25
0.7
100
100
7
0.09
NA
14.50
14.48
14.20
14.01
0.20
0.37
DP 5 to Pit D
6.7
168
168
193
5.2
100
23
15
0.66
NA
14.60
14.48
14.30
14.01
0.20
0.37
Pit D to Pit E
11.3
126
50
243
6.5
150
31
37
0.37
0.02
14.48
14.40
13.99
13.63
0.34
0.62
Pit E to Street Pit
5.7
251
35
240
2256
60.2
225
25
120
1.51
0.02
14.40
—
13.61
13.38
0.57
—
Sums =
1344
914 224
T PTrFxin-
Total area =
2482 m^
U/S = upstream
D/S = downstream
NA == not applicable
N
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A S/NZS 3500.3:2003
APPENDIX L
EXAMPLE CALCULATION—PUMPED SYSTEM
(Informative)
1000 m =0.1 ha
1 years
120 min
44.4 mm/h
0.9
LOCATION—BRISBANE
Contributing area (A) =
ARI
Storm period (T) =
Rainfall intensity (/) =
Coeffieient of run-off (Cro) ==
Peak discharge calculated using the rational method:
Q = CoX/= 0-9x44.4
Q = 39.96 (say 40 L/h/m')
Volume for 2 h storm:
V = QxTxA -(40/ 1000)x 2 X 1000 =80 m^^
ALTERNATIVE PUMP CAPACITY— WET WELL VOLUME COMBINATIONS
Site Area
1000 m'
Combined effective storage volume 80 m"^
Pump capacity
(Lis)
Volume pumped in 30 min
Required wet well volume
40
72
10
30
54
26
20
36
44
10 (min)
18
62
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A S/M/.S 3500.3:2003
174
Pump discharge
Overflow
^
Design wet
well storage
capacity
OFL
4—!- 1 HLAL
tlOO 1
-J~4 + IL Inlet
100
t
Design TWL
Pump start
Pump stop
100
-LLAL
topi ^
Inlet
V^PCs
(>-
NOTES:
OFL
HLAL =
LLAL =
^10/120 -
PC30 ~
PC5 -
•^ = V10/120 - PC
30
or < 1% catchment area
or < 3 m^
Overflow level
High-level alarm level
Low-level alarm level
Volume in 10 year ARI, 120 minute storm
Pump capacity over 30 min
Pump capacity over 5 min
DIMENSIONS IN MILLIMETRES
FIGURE L1 PUMP SYSTEM EXAMPLE
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175 AS/NZS 3500.3:2003
APPENDIX M
SUBSOIL DRAINAGE SYSTEMS—DESIGN
(Informative)
Ml SCOPE
This Appendix provides guidance for the design of subsoil drainage systems. Because
decisions are dependent on particular site or soil conditions, detailed design of such systems
is complex and, unless otherwise required to be authorized by the regulatory authority,
should be undertaken with advice from a suitably qualified competent person.
NOTES:
1 This Appendix does not cover—
(a) the subsurface drainage of large areas of land, such as playing fields;
(b) systems for removal of stormwater by adsorption or infiltration into permeable soils;
and
(c) drainage systems behind retaining walls.
2 An example of a suitable qualified competent person is a professional engineer specializing in
geotechnical engineering.
M2 PURPOSE
The purpose of the subsoil systems covered in this Standard is to drain away ground water
and, possibly, surface water in the vicinity of buildings in order to —
(a) increase the stability of the ground and footings of buildings by inducing a more
stable moisture regime and reducing foundation movements due to variations in the
soil moisture content;
(b) mitigate surface water ponding and waterlogging of soils by lowering watertables;
(c) increase soil strength by reducing its moisture content; and
(d) prevent damage, where applicable, due to frost heave of subsoil. (This generally
applies to sites 1 000 m or more above sea level.)
The investigation and design of subsoil drainage systems are uncertain processes. Only in a
very limited number of situations can the need for subsoil drainage be identified without
detailed subsurface investigations involving excavations, field observations and soil tests.
One important factor indicating a need for subsoil drainage is the presence of a watertable
high enough to have an adverse effect on the development.
In clay soils, subsoil drains can alter long-term soil moisture regimes so that building
foundations are adversely affected by removing water, or in some cases by introducing
water. In such conditions, subsoil drains should only be used where there are no other
options for solving a dampness problem.
>JOTE: Consideration should be given to the possible effects of intermittent or. permanent
reduction in ground water levels on adjacent lands. In soils with a clay content exceeding 20%,
lowering w^atertables can cause soil shrinkage and damage to structures. AS 2870.1 recommends
against placing subsoil drains too close to buildings on clayey sites.
m:3 types
The types of subsoil drains commonly used are shown in Figure Ml . These may be installed
on flat ground, in a sag or depression, or on sloping ground. The basic parts of a subsoil
drain are shown in Figure Ml (a) — a trench and fill or filter material, commonly sand or
gravel. This simple arrangement is called a rubble drain or French drain.
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AS/N/.S 3500.3:2003
176
Figure Mi(b) shows the addition of a geotextile lining to prevent external fine soil particles
being washed into the filter material and clogging it. Figure M 1(c) shows the addition of a
pipe to promote more rapid drainage. This is a typical subsoil drain. The pipe is perforated
to allow easy entry of water and can be rigid or flexible. Figure Ml(d) shows two further
variations — an impervious cap for situations where the drain is intended to collect only
subsurface flows, and bedding material for cases where the base of the excavation is
unsuitable as a pipe support.
Figures M 1(e), (f) and (g) show more elaboration. The pipe can be wrapped in geotextile to
prevent piping and loss of filter material. Geocomposite drains of various configurations
and manufacture can be provided. These are usually of plastic wrapped in geotextile and
various proprietary systems are available. Finally, Figure Ml(h) shows an external layer of
filter material provided around the geotextile encompassing the filter material. This might
be used where there is a likelihood of fine particles or deposits, e.g. iron precipitates,
clogging the geotextile.
In general, subsoil drains connect into a pit, which is part of a surface water drainage
system, with the subsoil drain pipe or strip drain penetrating the pit wall. Weepholes with a
suitable geotextile filter may also be used to admit water from the filter materials into the
pit.
■ Fill or ;
filter
:^material
Trench
(a)
Basic sys
[em
Pervious backfil
'////////////////j
^
0^^^yj^y^>y^/^^>J
(bl Geotextile filter
y//////////^/:///,
Y///////r////u/^
(c) Pipe drain
Impervious cap-\^
y)^////'/y>/////\
^j^jyy^jjjy/jj>}A
(d) Pipe drain with bedding,
excluding surface water
y/////////^//////
■Pipe wrapped
in geotextile -■
yyy/y//y//yA
1. .
W//?mf/A Vertical
geocomposite
drain
Horizontal
geocomposite
drain
Pervious filter layer
on trench sides
(el Geotextile
around pipe
(f) Geocomposite
drain in
narrow trench
(g) Geocomposite
drain in
shallow trench
(h) Soil filter layer
avoid clogging of
geotextile
to
FIGURE M1 TYPES OF SUBSOIL DRAINS
M4 LAYOUT
1V14.1 General arrangement
Relevant layouts for the types of subsoil drainage systems covered here include —
(a) subsoil drains on one or more sides of a building or cutting, including cut-off drains
for interception of ground water flows from higher land; and
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177
AS/NZS 3500.3:2003
(b) drainage systems for mitigating waterlogging or lowering watertables on small to
medium areas of land, e.g. less than 500 m".
These may involve branch subsoil drains connecting to a main subsoil drain. Main subsoil
drains often follow natural depressions.
The layout is directly related to the topography, the location of buildings and access points,
the geology (nature of subsoil and level of ground water) and area of a property. Subsoil
drains shall connect to a stormwater pit or a point of connection, and be consistent with the
layouts for the site stormwater drain and the external stormwater drainage network.
Suggested maximum spacings for branch subsoil drains are as given in Table M I .
TABLE Ml
SUGGESTED MAXIMUM SPACING OF BRANCH SUBSOIL DRAINS
Soil type
Depth of invert of main subsoil drains
0.8 to 1.0 m
1.0 to 1.5 ni
IVIaxiniuni spacing, ni
Sand
Sandy loam
Loam
Clay loam
Sandy clay
Clay
16 to 20
12 to 16
6 to 12
2 to 6
45 to 90
30 to 45
20 to 30
15 to 20
Source: BS 8301:1985
M4.2 Specifications — Drains
Subsoil drains should —
(a) be laid with even gradients and straight runs, with a minimum number of changes to
these and with any changes made at an appropriate fitting or at a pit;
(b) have a cover as specified in Clause 7.2.6;
(c) where under or in proximity to buildings, comply with Clause 7.2.9;
(d) where in proximity to other services, comply with Clause 7.2.7;
(e) be sized in accordance with Paragraph M5; and
(f) have clean-out points, as specified in Clause 7.4.1(c).
M4.3 Specifications — Filters
Filter materials and geotextiles shall be as specified in Clause 2.13.
MS DESIGN CONSIDERATIONS
M5.1 Drain dimensions and spacings
The depth of a subsoil drain is dictated by either the ground water conditions or the amount
by which the ground water level is to be lowered. The following criteria are recommended:
(a) Interceptor drains that aim to remove flows from a particular soil stratum or an
aquifer should completely penetrate the stratum and should extend to a depth of
1 50 mm to 300 mm into the impervious strata below.
(b) Where the subsoil drain is intended to lower the general ground water level, the
determination of the depth of drain depends on whether there is a single or a multi-
drain system as shown in Figure M2,
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AS/NZS 3500.3:2003
178
Analysis in these cases depends on knowledge of the hydraulic properties of the soil,
and on theoretical solutions. A professional engineer with geotechnical expertise shall
carry out the design work in critical cases.
For less critical situations, the drawdown curve for a single drain can be assumed to
have the characteristics given in Table M2.
For multi-drain systems, the drain spacings given in Table M3 can be used in less
critical applications.
Clay soils present particular problems as they may be too impermeable for any
drawdown to occur and expert geotechnical advice should be sought.
(c) Trench widths be a minimum of 300 mm where circular pipes are used. A minimum
width of 450 mm is required where human access is required. Where a trench is
deeper than 1.5 m, shoring as specified by relevant construction safety acts and
regulations shall be used.
For geocomposite drains set vertically, as shown in Figure 6.1(f), the minimum trench
width shall be 100 mm.
(d) Drains be constructed with the base of the trench at an even slope, so that the trench
acts as a rubble drain even if the pipe or geocomposite drain is blocked.
(e) Where a subsoil drain pipe or geocomposite drain connects to a pit or a pump-out
sump, there be access for easy inspection of flows so that the performance of the
subsoil drain can be monitored. For drains in critical locations, a means of
backflushing be provided to clear blockages.
(1) Subsoil drains not be directly connected to street kerbs and gutters, or to street
stormwater drains, in cases where backflow might cause damage.
Zone of influence
Drain spacing
Cl
/- Original
groundwater
level ■— -"
Drawdown
curve
Underlying
stratum
(a) Single drain
(b) Multi-drain
FIGURE M2 WATER TABLE DRAWDOWNS TO SINGLE AND MULTI-DRAIN SYSTEMS
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AS/NZS 3500.3:2003
TABLE 1V12
TYPICAL DRAWDOWN VALUES ASSOCIATED WITH A SINGLE DRAIN
Soil type
Zone of influence
ni
Typical gradient of
drawdown curve
Coarse gravel
150
— '
Medium gravel
50
200 to 1:100
Course sand
40
100 to 1:33
Medium sand
15 to 30
50 to 1 :20
Fine sand
8 to 15
20 to 1:5
Silt/elay
Variable
5 to 1 :2.5
TABLE M3
TYPICAL DRAIN SPACING S
Soil type
Depth
m
Spacing
m
Sand
1 to 2
50 to 90
Sandy loam
1 to 1.5
30 to 40
Clay loam (i.e., a clayey silt)
0.5 to 1
1 2 to 1 6
M5.2 Design of conduits
Pipes or other conduits associated with subsoil drains should meet the following criteria:
(a) The size of conduits be related to the expected flows through them. These flows will
be very small in fine-grained soils, but will be larger where —
(i) the drain is located in a pervious stratum such as a sand that is permanently fed
by a nearby water body or by heavy rainfall over a prolonged period; or
(ii) the drain cuts off flow in an aquifer that is carrying a significant How.
(b) Where circular pipes are used in subsurface drains, normally, a minimum pipe size of
DN 50 is employed, with larger sizes required for long runs of drains or in situation
such as those described in Paragraph M5.2(a).
In cases of the larger flows described in Paragraph M5.2(a) advice shall be sought from a
professional engineer with geotechnical expertise.
M5.3 Pipe gradient
The gradients of subsoil drains should be determined by the topography of the site rather
than by consideration of self-cleansing velocities.
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AS/NZS 35003:2003 180
AMENDMENT CONTROL SHEET
AS/NZS 3500.3:2003
Amendment No. I (2006)
CORRECTION
SUMMARY: This Amendment applies to Clause 3.5.4, and Appendiees E, I and J.
Published on 28 July 2006.
Amendment No. 2 (2010)
CORRECTION
SUMMARY: This Amendment applies to Clause 5.4.9(c), Equation 5.4.9 and Figure 7.3.
Published on 26 March 2010.
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^
N B W ZEALAND
PA a H t \A/A A O T f. A H O A
AS/NZS 3500.3/Amdt 3/2012-06-21
STANDARDS AUSTRALIA/STANDARDS NEW ZEALAND
Amendment No. 3
to
AS/NZS 3500.3:2003
Plumbing and drainage
Part 3: Stormwater drainage
REVISED TEXT
The 2003 edition of AS/NZS 3500.3 is amended as follows; the amendments should be inserted in the
appropriate places.
SUMMARY: This Amendment applies Clauses 1.3.5, 2.4.1, 2.4.3, 4.4.4, 4.13.4 and 8.11.4, and Tables 4.2 and
4.3.
Published on 21 June 2012.
Approved for publication in New Zealand on behalf of the Standards Council of New Zealand on 8 June 2012.
AMDT Clause 1.3.5
No. 3
JUN Delete existing definition and replace with the following:
2012
A rainwater collection area whose dominant material has little or no effect on the chemical
composition of rainwater draining from it. Such materials include acrylic, fibreglass,
aluminium/zinc and aluminium/zinc/magnesium alloy-coated steel, glass, glazed tiles,
unplasticized polyvinyl chloride and pre-painted metal.
AMDT Clause 2.4.1
JUN Delete the first paragraph and replace with the following:
2012
Roof drainage system components made from aluminium alloys, aluminium/zinc and
aluminium/zinc/magnesium alloy-coated steel, copper, copper alloys, zinc-coated steel,
stainless steel and zinc shall comply with AS/NZS 2179.1.
AMDT Clause 2.4.3
JUN Delete existing text and notes and replace with the following:
2012
Accessories and fasteners manufactured from aluminium alloys, aluminium/zinc and
aluminium/zinc/magnesium alloy-coated steel, copper, copper alloys, zinc-coated steel,
stainless steel and zinc shall comply with AS/NZS 2179.1.
AMDT Clause 4.4.4
JUN Delete existing text and replace with the following:
2012
Bedding materials used in conjunction with roof drainage systems shall be chemically
compatible. Cement-based bedding may be used between tiles and valley gutters other than
those of exposed aluminium/zinc or aluminium/zinc/magnesium alloy-coated steel.
AMDT Table 4.2
JUN Delete existing Table, Legend and Notes, and replace with the following:
2012
ISBN (Print) 978-1-86975-411-2
ISBN (PDF) 978-1-86975-412-9
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Accessory or fastener material
Fastener material
Roof drainage
system
components and
any cladding
Aluminium
alloys
Copper and copper
alloys*
Stainless steel
(300 series)
Zinc-coated steel
and zinc
Aluminium/zinc and
aluminium/zinc/
magnesium alloy-
coated steel
Lead
Ceramic or
organic coated
material
Atmospheric classification
SI and VS
Mild
SI and VS
Mild
SI and VS
Mild
SI and VS
Mild
SI and VS
Mild
SI and VS
Mild
SI, VS and Mild
Aluminium
alloys
Yes
Yes
No
No
t
Yes
t
t
Yes
Yes
No
No
Yes
Copper and
copper alloys
No
No
Yes
Yes
No
Yes
No
No
No
No
No
Yes
Yes
Stainless steel
(300 series)
No
No
No
No
Yes
Yes
No
No
No
No
No
Yes
Yes
Zinc-coated steel
and zinc
Yes
Yes
No
No
No
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Aluminium/zinc
and
aluminium/zinc/
magnesium alloy-
coated steel
Yes
Yes
No
No
No
Yes
t
t
Yes
Yes
No
No
Yes
Lead §
No
No
Yes
Yes
Yes
Yes
No
Yes
No
No
Yes
Yes
Yes
* Includes monel metal rivets.
t Grade 316 in accordance with ASTM A240 is suitable.
J Unpainted zinc-coated steel and zinc are suitable for direct contact but should not receive drainage from an inert catchment.
§ Due to its toxicity, lead is not recommended for rainwater goods.
LEGEND:
SI, VS, Mild = severe industrial, very severe and mild classifications (see AS/NZS 2312).
Yes = acceptable — as a result of bimetallic contact, either no additional corrosion of rainwater goods will take place, or at the worst, only very slight additional
corrosion. It also implies that the degree of corrosion would not significantly shorten the service life.
No = not acceptable — moderate to severe corrosion of rainwater goods will occur, a condition which may result in a significant reduction in the service life.
NOTE: Unless adequate separation can be assured, prepainted rainwater goods should be considered in terms of the base metal or coated metal product.
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Table 4.3
Delete existing Table, Legend and Notes, and replace with the following:
Upper cladding or roof drainage system material
Lower roof
drainage system
material
Aluminium
alloys
Copper and
copper
alloys
Stainless steel
(300 series)
Zinc-coated
steel and
zinc
Aluminium/zinc and
aluminium/zinc/
magnesium
alloy-coated steel
Lead
Prepainted
metal
Roof tiles
Plastic
Glazed
Unglazed
Glass
Aluminium alloys
Yes
No
*
Yes
Yes
*
Yes
Yes
Yes
Yes
Yes
Copper and copper
alloys
*
Yes
*
*
*
Yes
*
Yes
Yes
Yes
Yes
Stainless steel
(300 series)
*
*
Yes
*
*
Yes
*
Yes
Yes
Yes
Yes
Zinc-coated steel
and zinc
No
No
No
Yes
No
*
No
No
Yes
No
No
Aluminium/zinc
and
aluminium/zinc/
magnesium alloy-
coated steel
Yes
No
*
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes
Lead
*
*
*
*
*
Yes
*
Yes
Yes
Yes
Yes
* Whilst drainage between the materials shown would be acceptable, direct material contact should be avoided (see Table 4.2).
LEGEND:
Yes = acceptable
No = not acceptable
NOTE: 'Acceptable' and 'not acceptable' imply similar performances to those noted in Table 4.2.
o
c
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AMDT Clause 4.13.4
jUN Delete Clause heading and text and replace with the following:
2012
4.13.4 Aluminium/zinc and aluminium/zinc/magnesium alloy-coated steel
Aluminium/zinc and aluminium/zinc/magnesium alloy-coated steel components, including
accessories, shall be jointed with sealant joints and fasteners as specified in
Clause 4.13.1.2.
AMDT Clause 8.11.4
JUN Delete existing text and replace with the following:
2012
Storages shall be constructed of concrete, masonry, aluminium/zinc and
aluminium/zinc/magnesium alloy-coated steel, zinc-coated steel, galvanized iron or plastics.
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